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	$90.30	3.512%	$93.4713	$93.47	$93.45	$93.50
Purchase #2	$77.39	8.466%	$83.9418	$83.94	$83.95	$83.90
Purchase #3	$119.60	10.490%	$132.146	$132.15	$132.15	$132.10
Purchase #4	$30.34	7.230%	$32.5336	$32.53	$32.55	$32.50
Purchase #5	$86.69	8.846%	$94.3586	$94.36	$94.35	$94.40
Purchase #6	$116.57	10.265%	$128.5359	$128.54	$128.55	$128.50
Purchase #7	$149.31	12.251%	$167.602	$167.60	$167.60	$167.60
7 purchase totals =	$670.20		$732.5892	$732.59	$732.60	$732.50