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	$228.69	9.655%	$250.77	$250.77	$250.75	$250.80
Purchase #2	$125.37	6.700%	$133.7698	$133.77	$133.75	$133.80
Purchase #3	$130.47	8.165%	$141.1229	$141.12	$141.10	$141.10
Purchase #4	$118.57	7.571%	$127.5469	$127.55	$127.55	$127.50
Purchase #5	$182.62	4.742%	$191.2798	$191.28	$191.30	$191.30
Purchase #6	$100.82	12.209%	$113.1291	$113.13	$113.15	$113.10
Purchase #7	$227.32	13.295%	$257.5422	$257.54	$257.55	$257.50
7 purchase totals =	$1,113.86		$1,215.1607	$1,215.16	$1,215.15	$1,215.10