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	$74.62	5.164%	$78.4734	$78.47	$78.45	$78.50
Purchase #2	$104.31	12.823%	$117.6857	$117.69	$117.70	$117.70
Purchase #3	$33.84	3.218%	$34.929	$34.93	$34.95	$34.90
Purchase #4	$232.85	5.450%	$245.5403	$245.54	$245.55	$245.50
Purchase #5	$131.34	8.711%	$142.781	$142.78	$142.80	$142.80
Purchase #6	$19.34	9.436%	$21.1649	$21.16	$21.15	$21.20
Purchase #7	$224.65	13.216%	$254.3397	$254.34	$254.35	$254.30
7 purchase totals =	$820.95		$894.9140	$894.91	$894.95	$894.90