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	$95.41	9.154%	$104.1438	$104.14	$104.15	$104.10
Purchase #2	$38.76	9.301%	$42.3651	$42.37	$42.35	$42.40
Purchase #3	$105.57	6.243%	$112.1607	$112.16	$112.15	$112.20
Purchase #4	$161.93	8.177%	$175.171	$175.17	$175.15	$175.20
Purchase #5	$113.31	13.552%	$128.6658	$128.67	$128.65	$128.70
Purchase #6	$41.82	8.394%	$45.3304	$45.33	$45.35	$45.30
Purchase #7	$135.97	11.421%	$151.4991	$151.50	$151.50	$151.50
7 purchase totals =	$692.77		$759.3359	$759.34	$759.30	$759.40