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	$132.56	7.320%	$142.2634	$142.26	$142.25	$142.30
Purchase #2	$44.64	8.465%	$48.4188	$48.42	$48.40	$48.40
Purchase #3	$89.28	5.368%	$94.0726	$94.07	$94.05	$94.10
Purchase #4	$140.74	10.309%	$155.2489	$155.25	$155.25	$155.20
Purchase #5	$100.65	4.797%	$105.4782	$105.48	$105.50	$105.50
Purchase #6	$34.85	4.569%	$36.4423	$36.44	$36.45	$36.40
Purchase #7	$173.63	10.336%	$191.5764	$191.58	$191.60	$191.60
7 purchase totals =	$716.35		$773.5006	$773.50	$773.50	$773.50