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	$190.70	12.323%	$214.2	$214.20	$214.20	$214.20
Purchase #2	$125.70	12.549%	$141.4741	$141.47	$141.45	$141.50
Purchase #3	$55.84	6.260%	$59.3356	$59.34	$59.35	$59.30
Purchase #4	$90.61	9.192%	$98.9389	$98.94	$98.95	$98.90
Purchase #5	$231.44	13.522%	$262.7353	$262.74	$262.75	$262.70
Purchase #6	$98.57	13.501%	$111.8779	$111.88	$111.90	$111.90
Purchase #7	$78.77	6.274%	$83.712	$83.71	$83.70	$83.70
7 purchase totals =	$871.63		$972.2738	$972.28	$972.30	$972.20