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	$90.32	12.748%	$101.834	$101.83	$101.85	$101.80
Purchase #2	$182.91	5.378%	$192.7469	$192.75	$192.75	$192.70
Purchase #3	$39.90	5.613%	$42.1396	$42.14	$42.15	$42.10
Purchase #4	$166.32	3.634%	$172.3641	$172.36	$172.35	$172.40
Purchase #5	$236.58	4.745%	$247.8057	$247.81	$247.80	$247.80
Purchase #6	$238.76	10.109%	$262.8962	$262.90	$262.90	$262.90
Purchase #7	$64.56	11.182%	$71.7791	$71.78	$71.80	$71.80
7 purchase totals =	$1,019.35		$1,091.5656	$1,091.57	$1,091.60	$1,091.50