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	$126.98	12.372%	$142.69	$142.69	$142.70	$142.70
Purchase #2	$129.25	11.200%	$143.726	$143.73	$143.75	$143.70
Purchase #3	$225.88	13.553%	$256.4935	$256.49	$256.50	$256.50
Purchase #4	$245.33	3.601%	$254.1643	$254.16	$254.15	$254.20
Purchase #5	$79.86	13.282%	$90.467	$90.47	$90.45	$90.50
Purchase #6	$20.37	11.119%	$22.6349	$22.63	$22.65	$22.60
Purchase #7	$185.28	8.187%	$200.4489	$200.45	$200.45	$200.40
7 purchase totals =	$1,012.95		$1,110.6246	$1,110.62	$1,110.65	$1,110.60