Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$145.96	7.779%	$157.3142	$157.31	$157.30	$157.30
Purchase #2	$148.30	11.164%	$164.8562	$164.86	$164.85	$164.90
Purchase #3	$130.83	10.646%	$144.7582	$144.76	$144.75	$144.80
Purchase #4	$241.45	11.570%	$269.3858	$269.39	$269.40	$269.40
Purchase #5	$165.47	10.532%	$182.8973	$182.90	$182.90	$182.90
Purchase #6	$218.31	9.745%	$239.5843	$239.58	$239.60	$239.60
Purchase #7	$129.44	11.296%	$144.0615	$144.06	$144.05	$144.10
7 purchase totals =	$1,179.76		$1,302.8575	$1,302.86	$1,302.85	$1,303.00