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	$210.38	5.495%	$221.9404	$221.94	$221.95	$221.90
Purchase #2	$196.73	7.487%	$211.4592	$211.46	$211.45	$211.50
Purchase #3	$15.82	13.179%	$17.9049	$17.90	$17.90	$17.90
Purchase #4	$66.50	6.834%	$71.0446	$71.04	$71.05	$71.00
Purchase #5	$224.47	11.444%	$250.1583	$250.16	$250.15	$250.20
Purchase #6	$152.50	7.657%	$164.1769	$164.18	$164.20	$164.20
Purchase #7	$50.83	7.305%	$54.5431	$54.54	$54.55	$54.50
7 purchase totals =	$917.23		$991.2274	$991.22	$991.25	$991.20