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	$134.34	5.629%	$141.902	$141.90	$141.90	$141.90
Purchase #2	$25.29	3.246%	$26.1109	$26.11	$26.10	$26.10
Purchase #3	$204.37	6.815%	$218.2978	$218.30	$218.30	$218.30
Purchase #4	$123.91	6.429%	$131.8762	$131.88	$131.90	$131.90
Purchase #5	$100.67	10.733%	$111.4749	$111.47	$111.45	$111.50
Purchase #6	$151.35	3.411%	$156.5125	$156.51	$156.50	$156.50
Purchase #7	$67.40	12.207%	$75.6275	$75.63	$75.65	$75.60
7 purchase totals =	$807.33		$861.8018	$861.80	$861.80	$861.80