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	$207.46	4.621%	$217.0467	$217.05	$217.05	$217.00
Purchase #2	$103.34	3.437%	$106.8918	$106.89	$106.90	$106.90
Purchase #3	$53.49	11.432%	$59.605	$59.61	$59.60	$59.60
Purchase #4	$108.47	13.438%	$123.0462	$123.05	$123.05	$123.00
Purchase #5	$175.52	10.624%	$194.1672	$194.17	$194.15	$194.20
Purchase #6	$138.98	12.585%	$156.4706	$156.47	$156.45	$156.50
Purchase #7	$88.33	6.799%	$94.3356	$94.34	$94.35	$94.30
7 purchase totals =	$875.59		$951.5631	$951.58	$951.55	$951.50