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	$174.50	4.457%	$182.2775	$182.28	$182.30	$182.30
Purchase #2	$46.52	9.141%	$50.7724	$50.77	$50.75	$50.80
Purchase #3	$63.31	11.748%	$70.7477	$70.75	$70.75	$70.70
Purchase #4	$242.63	10.203%	$267.3855	$267.39	$267.40	$267.40
Purchase #5	$100.42	4.372%	$104.8104	$104.81	$104.80	$104.80
Purchase #6	$171.49	5.482%	$180.8911	$180.89	$180.90	$180.90
Purchase #7	$142.87	6.740%	$152.4994	$152.50	$152.50	$152.50
7 purchase totals =	$941.74		$1,009.3840	$1,009.39	$1,009.40	$1,009.40