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	$239.85	4.614%	$250.9167	$250.92	$250.90	$250.90
Purchase #2	$76.82	8.500%	$83.3497	$83.35	$83.35	$83.30
Purchase #3	$167.89	8.188%	$181.6368	$181.64	$181.65	$181.60
Purchase #4	$151.86	12.113%	$170.2548	$170.25	$170.25	$170.30
Purchase #5	$63.35	13.742%	$72.0556	$72.06	$72.05	$72.10
Purchase #6	$143.70	8.405%	$155.778	$155.78	$155.80	$155.80
Purchase #7	$224.39	7.790%	$241.87	$241.87	$241.85	$241.90
7 purchase totals =	$1,067.86		$1,155.8616	$1,155.87	$1,155.85	$1,155.90