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	$236.80	3.306%	$244.6286	$244.63	$244.65	$244.60
Purchase #2	$86.69	5.625%	$91.5663	$91.57	$91.55	$91.60
Purchase #3	$238.68	6.119%	$253.2848	$253.28	$253.30	$253.30
Purchase #4	$51.65	5.504%	$54.4928	$54.49	$54.50	$54.50
Purchase #5	$164.82	10.497%	$182.1212	$182.12	$182.10	$182.10
Purchase #6	$134.42	13.785%	$152.9498	$152.95	$152.95	$152.90
Purchase #7	$191.95	4.491%	$200.5705	$200.57	$200.55	$200.60
7 purchase totals =	$1,105.01		$1,179.6140	$1,179.61	$1,179.60	$1,179.60