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	$180.80	12.429%	$203.2716	$203.27	$203.25	$203.30
Purchase #2	$75.42	3.823%	$78.3033	$78.30	$78.30	$78.30
Purchase #3	$60.90	10.306%	$67.1764	$67.18	$67.20	$67.20
Purchase #4	$32.92	7.342%	$35.337	$35.34	$35.35	$35.30
Purchase #5	$159.81	6.284%	$169.8525	$169.85	$169.85	$169.90
Purchase #6	$111.49	12.199%	$125.0907	$125.09	$125.10	$125.10
Purchase #7	$67.67	7.380%	$72.664	$72.66	$72.65	$72.70
7 purchase totals =	$689.01		$751.6955	$751.69	$751.70	$751.80