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	$135.89	11.421%	$151.41	$151.41	$151.40	$151.40
Purchase #2	$130.43	13.383%	$147.8854	$147.89	$147.90	$147.90
Purchase #3	$66.33	9.561%	$72.6718	$72.67	$72.65	$72.70
Purchase #4	$140.96	5.649%	$148.9228	$148.92	$148.90	$148.90
Purchase #5	$126.74	6.108%	$134.4813	$134.48	$134.50	$134.50
Purchase #6	$201.60	13.756%	$229.3321	$229.33	$229.35	$229.30
Purchase #7	$54.43	6.529%	$57.9837	$57.98	$58.00	$58.00
7 purchase totals =	$856.38		$942.6871	$942.68	$942.70	$942.70