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	$94.27	6.199%	$100.1138	$100.11	$100.10	$100.10
Purchase #2	$185.80	13.145%	$210.2234	$210.22	$210.20	$210.20
Purchase #3	$154.75	4.140%	$161.1567	$161.16	$161.15	$161.20
Purchase #4	$223.54	4.552%	$233.7155	$233.72	$233.70	$233.70
Purchase #5	$223.52	11.595%	$249.4371	$249.44	$249.45	$249.40
Purchase #6	$35.85	10.345%	$39.5587	$39.56	$39.55	$39.60
Purchase #7	$197.82	9.534%	$216.6802	$216.68	$216.70	$216.70
7 purchase totals =	$1,115.55		$1,210.8854	$1,210.89	$1,210.85	$1,210.90