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	$115.63	7.153%	$123.901	$123.90	$123.90	$123.90
Purchase #2	$219.27	7.626%	$235.9915	$235.99	$236.00	$236.00
Purchase #3	$121.29	7.646%	$130.5638	$130.56	$130.55	$130.60
Purchase #4	$106.67	10.166%	$117.5141	$117.51	$117.50	$117.50
Purchase #5	$75.51	10.593%	$83.5088	$83.51	$83.50	$83.50
Purchase #6	$55.46	7.475%	$59.6056	$59.61	$59.60	$59.60
Purchase #7	$184.48	5.291%	$194.2408	$194.24	$194.25	$194.20
7 purchase totals =	$878.31		$945.3256	$945.32	$945.30	$945.30