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	$121.96	8.711%	$132.5839	$132.58	$132.60	$132.60
Purchase #2	$127.29	3.659%	$131.9475	$131.95	$131.95	$131.90
Purchase #3	$158.86	10.465%	$175.4847	$175.48	$175.50	$175.50
Purchase #4	$134.98	8.339%	$146.236	$146.24	$146.25	$146.20
Purchase #5	$55.26	9.573%	$60.55	$60.55	$60.55	$60.60
Purchase #6	$153.77	3.114%	$158.5584	$158.56	$158.55	$158.60
Purchase #7	$78.63	5.700%	$83.1119	$83.11	$83.10	$83.10
7 purchase totals =	$830.75		$888.4724	$888.47	$888.50	$888.50