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	$235.85	11.475%	$262.9138	$262.91	$262.90	$262.90
Purchase #2	$181.44	4.467%	$189.5449	$189.54	$189.55	$189.50
Purchase #3	$53.45	11.343%	$59.5128	$59.51	$59.50	$59.50
Purchase #4	$177.85	7.527%	$191.2368	$191.24	$191.25	$191.20
Purchase #5	$130.57	10.114%	$143.7758	$143.78	$143.80	$143.80
Purchase #6	$106.46	13.482%	$120.8129	$120.81	$120.80	$120.80
Purchase #7	$243.76	11.491%	$271.7705	$271.77	$271.75	$271.80
7 purchase totals =	$1,129.38		$1,239.5675	$1,239.56	$1,239.55	$1,239.50