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	$119.50	9.127%	$130.4068	$130.41	$130.40	$130.40
Purchase #2	$72.75	3.796%	$75.5116	$75.51	$75.50	$75.50
Purchase #3	$34.61	6.722%	$36.9365	$36.94	$36.95	$36.90
Purchase #4	$55.97	9.865%	$61.4914	$61.49	$61.50	$61.50
Purchase #5	$64.44	5.330%	$67.8747	$67.87	$67.85	$67.90
Purchase #6	$99.85	11.535%	$111.3677	$111.37	$111.35	$111.40
Purchase #7	$34.55	8.148%	$37.3651	$37.37	$37.35	$37.40
7 purchase totals =	$481.67		$520.9538	$520.96	$520.90	$521.00