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	$87.96	10.442%	$97.1448	$97.14	$97.15	$97.10
Purchase #2	$159.62	4.344%	$166.5539	$166.55	$166.55	$166.60
Purchase #3	$177.27	6.579%	$188.9326	$188.93	$188.95	$188.90
Purchase #4	$146.48	13.247%	$165.8842	$165.88	$165.90	$165.90
Purchase #5	$168.32	12.462%	$189.296	$189.30	$189.30	$189.30
Purchase #6	$89.48	6.298%	$95.1155	$95.12	$95.10	$95.10
Purchase #7	$53.29	11.591%	$59.4668	$59.47	$59.45	$59.50
7 purchase totals =	$882.42		$962.3938	$962.39	$962.40	$962.40