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	$42.79	5.795%	$45.2697	$45.27	$45.25	$45.30
Purchase #2	$97.47	7.517%	$104.7968	$104.80	$104.80	$104.80
Purchase #3	$21.71	4.805%	$22.7532	$22.75	$22.75	$22.80
Purchase #4	$212.91	4.505%	$222.5016	$222.50	$222.50	$222.50
Purchase #5	$177.54	4.518%	$185.5613	$185.56	$185.55	$185.60
Purchase #6	$34.74	4.739%	$36.3863	$36.39	$36.40	$36.40
Purchase #7	$188.55	13.191%	$213.4216	$213.42	$213.40	$213.40
7 purchase totals =	$775.71		$830.6905	$830.69	$830.65	$830.80