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	$206.77	5.574%	$218.2954	$218.30	$218.30	$218.30
Purchase #2	$95.39	4.538%	$99.7188	$99.72	$99.70	$99.70
Purchase #3	$73.89	10.223%	$81.4438	$81.44	$81.45	$81.40
Purchase #4	$235.79	11.246%	$262.3069	$262.31	$262.30	$262.30
Purchase #5	$42.81	7.663%	$46.0905	$46.09	$46.10	$46.10
Purchase #6	$153.27	10.562%	$169.4584	$169.46	$169.45	$169.50
Purchase #7	$168.80	11.263%	$187.8119	$187.81	$187.80	$187.80
7 purchase totals =	$976.72		$1,065.1257	$1,065.13	$1,065.10	$1,065.10