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	$113.51	8.748%	$123.4399	$123.44	$123.45	$123.40
Purchase #2	$154.77	8.393%	$167.7598	$167.76	$167.75	$167.80
Purchase #3	$64.89	10.405%	$71.6418	$71.64	$71.65	$71.60
Purchase #4	$34.76	12.191%	$38.9976	$39.00	$39.00	$39.00
Purchase #5	$137.81	10.672%	$152.5171	$152.52	$152.50	$152.50
Purchase #6	$223.48	9.361%	$244.4	$244.40	$244.40	$244.40
Purchase #7	$246.58	7.179%	$264.282	$264.28	$264.30	$264.30
7 purchase totals =	$975.80		$1,063.0382	$1,063.04	$1,063.05	$1,063.00