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	$33.38	12.370%	$37.5091	$37.51	$37.50	$37.50
Purchase #2	$189.63	5.320%	$199.7183	$199.72	$199.70	$199.70
Purchase #3	$152.83	12.391%	$171.7672	$171.77	$171.75	$171.80
Purchase #4	$158.34	11.757%	$176.956	$176.96	$176.95	$177.00
Purchase #5	$106.46	4.136%	$110.8632	$110.86	$110.85	$110.90
Purchase #6	$172.60	4.407%	$180.2065	$180.21	$180.20	$180.20
Purchase #7	$143.60	11.122%	$159.5712	$159.57	$159.55	$159.60
7 purchase totals =	$956.84		$1,036.5915	$1,036.60	$1,036.50	$1,036.70