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	$235.57	11.184%	$261.9161	$261.92	$261.90	$261.90
Purchase #2	$116.31	4.105%	$121.0845	$121.08	$121.10	$121.10
Purchase #3	$33.54	12.291%	$37.6624	$37.66	$37.65	$37.70
Purchase #4	$120.85	3.281%	$124.8151	$124.82	$124.80	$124.80
Purchase #5	$170.48	12.107%	$191.12	$191.12	$191.10	$191.10
Purchase #6	$199.69	5.240%	$210.1538	$210.15	$210.15	$210.20
Purchase #7	$223.81	13.415%	$253.8341	$253.83	$253.85	$253.80
7 purchase totals =	$1,100.25		$1,200.5860	$1,200.58	$1,200.55	$1,200.60