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	$195.90	13.286%	$221.9273	$221.93	$221.95	$221.90
Purchase #2	$225.78	12.814%	$254.7114	$254.71	$254.70	$254.70
Purchase #3	$79.87	12.793%	$90.0878	$90.09	$90.10	$90.10
Purchase #4	$132.41	5.577%	$139.7945	$139.79	$139.80	$139.80
Purchase #5	$92.98	11.637%	$103.8001	$103.80	$103.80	$103.80
Purchase #6	$116.29	6.507%	$123.857	$123.86	$123.85	$123.90
Purchase #7	$247.46	11.784%	$276.6207	$276.62	$276.60	$276.60
7 purchase totals =	$1,090.69		$1,210.7988	$1,210.80	$1,210.80	$1,210.80