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	$90.38	10.190%	$99.5897	$99.59	$99.60	$99.60
Purchase #2	$55.36	11.743%	$61.8609	$61.86	$61.85	$61.90
Purchase #3	$184.27	8.192%	$199.3654	$199.37	$199.35	$199.40
Purchase #4	$240.54	12.429%	$270.4367	$270.44	$270.45	$270.40
Purchase #5	$55.98	6.133%	$59.4133	$59.41	$59.40	$59.40
Purchase #6	$206.34	10.167%	$227.3186	$227.32	$227.30	$227.30
Purchase #7	$100.83	5.359%	$106.2335	$106.23	$106.25	$106.20
7 purchase totals =	$933.70		$1,024.2181	$1,024.22	$1,024.20	$1,024.20