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	$202.80	12.857%	$228.874	$228.87	$228.85	$228.90
Purchase #2	$143.57	5.448%	$151.3917	$151.39	$151.40	$151.40
Purchase #3	$151.31	10.260%	$166.8344	$166.83	$166.85	$166.80
Purchase #4	$22.48	7.858%	$24.2465	$24.25	$24.25	$24.20
Purchase #5	$124.54	10.310%	$137.3801	$137.38	$137.40	$137.40
Purchase #6	$144.82	5.219%	$152.3782	$152.38	$152.40	$152.40
Purchase #7	$24.44	3.793%	$25.367	$25.37	$25.35	$25.40
7 purchase totals =	$813.96		$886.4719	$886.47	$886.50	$886.50