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	$189.46	4.114%	$197.2544	$197.25	$197.25	$197.30
Purchase #2	$59.51	11.261%	$66.2114	$66.21	$66.20	$66.20
Purchase #3	$191.58	12.399%	$215.334	$215.33	$215.35	$215.30
Purchase #4	$165.97	5.117%	$174.4627	$174.46	$174.45	$174.50
Purchase #5	$112.98	12.541%	$127.1488	$127.15	$127.15	$127.10
Purchase #6	$202.83	4.825%	$212.6165	$212.62	$212.60	$212.60
Purchase #7	$44.35	10.192%	$48.8702	$48.87	$48.85	$48.90
7 purchase totals =	$966.68		$1,041.8980	$1,041.89	$1,041.85	$1,041.90