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	$104.34	6.451%	$111.071	$111.07	$111.05	$111.10
Purchase #2	$65.88	8.106%	$71.2202	$71.22	$71.20	$71.20
Purchase #3	$244.32	13.728%	$277.8602	$277.86	$277.85	$277.90
Purchase #4	$52.75	10.173%	$58.1163	$58.12	$58.10	$58.10
Purchase #5	$44.77	12.787%	$50.4947	$50.49	$50.50	$50.50
Purchase #6	$135.56	10.761%	$150.1476	$150.15	$150.15	$150.10
Purchase #7	$203.92	3.399%	$210.8512	$210.85	$210.85	$210.90
7 purchase totals =	$851.54		$929.7612	$929.76	$929.70	$929.80