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	$67.82	4.174%	$70.6508	$70.65	$70.65	$70.70
Purchase #2	$91.87	6.344%	$97.6982	$97.70	$97.70	$97.70
Purchase #3	$57.35	8.484%	$62.2156	$62.22	$62.20	$62.20
Purchase #4	$237.79	7.261%	$255.0559	$255.06	$255.05	$255.10
Purchase #5	$50.60	11.157%	$56.2454	$56.25	$56.25	$56.20
Purchase #6	$38.70	6.560%	$41.2387	$41.24	$41.25	$41.20
Purchase #7	$75.30	11.388%	$83.8752	$83.88	$83.90	$83.90
7 purchase totals =	$619.43		$666.9798	$667.00	$667.00	$667.00