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	$167.45	7.161%	$179.4411	$179.44	$179.45	$179.40
Purchase #2	$189.65	12.580%	$213.508	$213.51	$213.50	$213.50
Purchase #3	$156.51	5.562%	$165.2151	$165.22	$165.20	$165.20
Purchase #4	$192.59	4.282%	$200.8367	$200.84	$200.85	$200.80
Purchase #5	$6.70	5.375%	$7.0601	$7.06	$7.05	$7.10
Purchase #6	$210.86	11.376%	$234.8474	$234.85	$234.85	$234.80
Purchase #7	$161.99	5.752%	$171.3077	$171.31	$171.30	$171.30
7 purchase totals =	$1,085.75		$1,172.2161	$1,172.23	$1,172.20	$1,172.10