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	$112.36	10.811%	$124.5072	$124.51	$124.50	$124.50
Purchase #2	$230.79	13.334%	$261.5635	$261.56	$261.55	$261.60
Purchase #3	$230.62	10.445%	$254.7083	$254.71	$254.70	$254.70
Purchase #4	$174.49	12.429%	$196.1774	$196.18	$196.20	$196.20
Purchase #5	$12.43	10.343%	$13.7156	$13.72	$13.70	$13.70
Purchase #6	$78.35	6.412%	$83.3738	$83.37	$83.35	$83.40
Purchase #7	$142.57	10.848%	$158.036	$158.04	$158.05	$158.00
7 purchase totals =	$981.61		$1,092.0818	$1,092.09	$1,092.05	$1,092.10