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	$68.61	4.814%	$71.9129	$71.91	$71.90	$71.90
Purchase #2	$168.50	12.691%	$189.8843	$189.88	$189.90	$189.90
Purchase #3	$174.58	8.565%	$189.5328	$189.53	$189.55	$189.50
Purchase #4	$71.89	9.504%	$78.7224	$78.72	$78.70	$78.70
Purchase #5	$97.81	13.600%	$111.1122	$111.11	$111.10	$111.10
Purchase #6	$224.43	13.408%	$254.5216	$254.52	$254.50	$254.50
Purchase #7	$48.81	7.212%	$52.3302	$52.33	$52.35	$52.30
7 purchase totals =	$854.63		$948.0164	$948.00	$948.00	$947.90