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	$11.27	11.157%	$12.5274	$12.53	$12.55	$12.50
Purchase #2	$69.75	5.292%	$73.4412	$73.44	$73.45	$73.40
Purchase #3	$120.74	5.873%	$127.8311	$127.83	$127.85	$127.80
Purchase #4	$144.89	7.771%	$156.1494	$156.15	$156.15	$156.10
Purchase #5	$243.64	4.388%	$254.3309	$254.33	$254.35	$254.30
Purchase #6	$158.54	7.477%	$170.394	$170.39	$170.40	$170.40
Purchase #7	$74.48	12.678%	$83.9226	$83.92	$83.90	$83.90
7 purchase totals =	$823.31		$878.5966	$878.59	$878.65	$878.40