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	$143.78	5.179%	$151.2264	$151.23	$151.25	$151.20
Purchase #2	$140.69	8.174%	$152.19	$152.19	$152.20	$152.20
Purchase #3	$83.25	8.246%	$90.1148	$90.11	$90.10	$90.10
Purchase #4	$99.83	9.580%	$109.3937	$109.39	$109.40	$109.40
Purchase #5	$97.26	7.645%	$104.6955	$104.70	$104.70	$104.70
Purchase #6	$112.74	3.148%	$116.2891	$116.29	$116.30	$116.30
Purchase #7	$232.52	8.166%	$251.5076	$251.51	$251.50	$251.50
7 purchase totals =	$910.07		$975.4171	$975.42	$975.45	$975.40