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	$105.63	11.421%	$117.694	$117.69	$117.70	$117.70
Purchase #2	$64.75	11.408%	$72.1367	$72.14	$72.15	$72.10
Purchase #3	$146.60	10.779%	$162.402	$162.40	$162.40	$162.40
Purchase #4	$170.95	12.733%	$192.7171	$192.72	$192.70	$192.70
Purchase #5	$37.64	4.334%	$39.2713	$39.27	$39.25	$39.30
Purchase #6	$80.67	3.399%	$83.412	$83.41	$83.40	$83.40
Purchase #7	$153.88	11.306%	$171.2777	$171.28	$171.30	$171.30
7 purchase totals =	$760.12		$838.9108	$838.91	$838.90	$838.90