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	$199.96	3.198%	$206.3547	$206.35	$206.35	$206.40
Purchase #2	$35.84	3.718%	$37.1725	$37.17	$37.15	$37.20
Purchase #3	$85.60	6.139%	$90.855	$90.86	$90.85	$90.90
Purchase #4	$120.67	10.447%	$133.2764	$133.28	$133.30	$133.30
Purchase #5	$19.41	9.366%	$21.2279	$21.23	$21.25	$21.20
Purchase #6	$129.51	10.191%	$142.7084	$142.71	$142.70	$142.70
Purchase #7	$104.58	4.167%	$108.9378	$108.94	$108.95	$108.90
7 purchase totals =	$695.57		$740.5327	$740.54	$740.55	$740.60