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	$247.85	5.524%	$261.5412	$261.54	$261.55	$261.50
Purchase #2	$196.37	7.485%	$211.0683	$211.07	$211.05	$211.10
Purchase #3	$154.69	6.521%	$164.7773	$164.78	$164.80	$164.80
Purchase #4	$178.34	3.194%	$184.0362	$184.04	$184.05	$184.00
Purchase #5	$140.52	7.606%	$151.208	$151.21	$151.20	$151.20
Purchase #6	$183.75	13.375%	$208.3266	$208.33	$208.35	$208.30
Purchase #7	$91.65	13.352%	$103.8871	$103.89	$103.90	$103.90
7 purchase totals =	$1,193.17		$1,284.8447	$1,284.86	$1,284.90	$1,284.80