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	$216.66	11.250%	$241.0343	$241.03	$241.05	$241.00
Purchase #2	$116.93	5.652%	$123.5389	$123.54	$123.55	$123.50
Purchase #3	$212.84	5.208%	$223.9247	$223.92	$223.90	$223.90
Purchase #4	$245.30	11.809%	$274.2675	$274.27	$274.25	$274.30
Purchase #5	$189.92	10.330%	$209.5387	$209.54	$209.55	$209.50
Purchase #6	$245.82	4.510%	$256.9065	$256.91	$256.90	$256.90
Purchase #7	$140.43	6.440%	$149.4737	$149.47	$149.45	$149.50
7 purchase totals =	$1,367.90		$1,478.6843	$1,478.68	$1,478.65	$1,478.60