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	$167.65	12.404%	$188.4453	$188.45	$188.45	$188.40
Purchase #2	$218.83	13.860%	$249.1598	$249.16	$249.15	$249.20
Purchase #3	$80.54	9.408%	$88.1172	$88.12	$88.10	$88.10
Purchase #4	$105.40	5.604%	$111.3066	$111.31	$111.30	$111.30
Purchase #5	$229.32	13.441%	$260.1429	$260.14	$260.15	$260.10
Purchase #6	$66.71	8.315%	$72.2569	$72.26	$72.25	$72.30
Purchase #7	$28.95	11.837%	$32.3768	$32.38	$32.40	$32.40
7 purchase totals =	$897.40		$1,001.8055	$1,001.82	$1,001.80	$1,001.80