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	$190.57	7.517%	$204.8951	$204.90	$204.90	$204.90
Purchase #2	$87.66	7.124%	$93.9049	$93.90	$93.90	$93.90
Purchase #3	$25.73	11.371%	$28.6558	$28.66	$28.65	$28.70
Purchase #4	$79.82	12.325%	$89.6578	$89.66	$89.65	$89.70
Purchase #5	$171.26	9.109%	$186.8601	$186.86	$186.85	$186.90
Purchase #6	$111.83	11.654%	$124.8627	$124.86	$124.85	$124.90
Purchase #7	$215.96	8.762%	$234.8824	$234.88	$234.90	$234.90
7 purchase totals =	$882.83		$963.7188	$963.72	$963.70	$963.90