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	$223.80	13.478%	$253.9638	$253.96	$253.95	$254.00
Purchase #2	$33.40	5.274%	$35.1615	$35.16	$35.15	$35.20
Purchase #3	$79.37	3.725%	$82.3265	$82.33	$82.35	$82.30
Purchase #4	$111.48	12.471%	$125.3827	$125.38	$125.40	$125.40
Purchase #5	$234.40	7.447%	$251.8558	$251.86	$251.85	$251.90
Purchase #6	$196.71	13.180%	$222.6364	$222.64	$222.65	$222.60
Purchase #7	$149.45	10.441%	$165.0541	$165.05	$165.05	$165.10
7 purchase totals =	$1,028.61		$1,136.3808	$1,136.38	$1,136.40	$1,136.50