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	$112.95	4.581%	$118.1242	$118.12	$118.10	$118.10
Purchase #2	$66.39	13.138%	$75.1123	$75.11	$75.10	$75.10
Purchase #3	$100.41	5.389%	$105.8211	$105.82	$105.80	$105.80
Purchase #4	$6.48	4.284%	$6.7576	$6.76	$6.75	$6.80
Purchase #5	$66.75	6.709%	$71.2283	$71.23	$71.25	$71.20
Purchase #6	$118.89	7.670%	$128.0089	$128.01	$128.00	$128.00
Purchase #7	$138.33	9.495%	$151.4644	$151.46	$151.45	$151.50
7 purchase totals =	$610.20		$656.5168	$656.51	$656.45	$656.50