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	$224.32	13.135%	$253.7844	$253.78	$253.80	$253.80
Purchase #2	$159.58	6.457%	$169.8841	$169.88	$169.90	$169.90
Purchase #3	$246.54	11.606%	$275.1534	$275.15	$275.15	$275.20
Purchase #4	$195.70	8.661%	$212.6496	$212.65	$212.65	$212.60
Purchase #5	$187.59	11.564%	$209.2829	$209.28	$209.30	$209.30
Purchase #6	$118.31	7.495%	$127.1773	$127.18	$127.20	$127.20
Purchase #7	$42.90	11.658%	$47.9013	$47.90	$47.90	$47.90
7 purchase totals =	$1,174.94		$1,295.8330	$1,295.82	$1,295.90	$1,295.90