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	$168.85	6.681%	$180.1309	$180.13	$180.15	$180.10
Purchase #2	$154.46	8.680%	$167.8671	$167.87	$167.85	$167.90
Purchase #3	$37.77	4.460%	$39.4545	$39.45	$39.45	$39.50
Purchase #4	$113.58	4.718%	$118.9387	$118.94	$118.95	$118.90
Purchase #5	$171.49	6.219%	$182.155	$182.16	$182.15	$182.20
Purchase #6	$169.94	10.720%	$188.1576	$188.16	$188.15	$188.20
Purchase #7	$187.89	12.155%	$210.728	$210.73	$210.75	$210.70
7 purchase totals =	$1,003.98		$1,087.4318	$1,087.44	$1,087.45	$1,087.50