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	$143.46	6.550%	$152.8566	$152.86	$152.85	$152.90
Purchase #2	$77.71	6.327%	$82.6267	$82.63	$82.65	$82.60
Purchase #3	$40.55	11.211%	$45.0961	$45.10	$45.10	$45.10
Purchase #4	$21.39	3.492%	$22.1369	$22.14	$22.15	$22.10
Purchase #5	$136.35	10.758%	$151.0185	$151.02	$151.00	$151.00
Purchase #6	$164.76	8.685%	$179.0694	$179.07	$179.05	$179.10
Purchase #7	$212.67	4.399%	$222.0254	$222.03	$222.05	$222.00
7 purchase totals =	$796.89		$854.8296	$854.85	$854.85	$854.80