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	$140.62	8.109%	$152.0229	$152.02	$152.00	$152.00
Purchase #2	$123.52	4.290%	$128.819	$128.82	$128.80	$128.80
Purchase #3	$157.32	13.383%	$178.3741	$178.37	$178.35	$178.40
Purchase #4	$77.77	7.172%	$83.3477	$83.35	$83.35	$83.30
Purchase #5	$58.31	4.832%	$61.1275	$61.13	$61.15	$61.10
Purchase #6	$72.67	5.362%	$76.5666	$76.57	$76.55	$76.60
Purchase #7	$164.75	11.405%	$183.5397	$183.54	$183.55	$183.50
7 purchase totals =	$794.96		$863.7975	$863.80	$863.75	$863.70