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	$89.59	4.829%	$93.9163	$93.92	$93.90	$93.90
Purchase #2	$125.33	11.178%	$139.3394	$139.34	$139.35	$139.30
Purchase #3	$151.93	8.741%	$165.2102	$165.21	$165.20	$165.20
Purchase #4	$137.41	10.227%	$151.4629	$151.46	$151.45	$151.50
Purchase #5	$132.58	13.583%	$150.5883	$150.59	$150.60	$150.60
Purchase #6	$166.74	4.678%	$174.5401	$174.54	$174.55	$174.50
Purchase #7	$250.42	11.129%	$278.2892	$278.29	$278.30	$278.30
7 purchase totals =	$1,054.00		$1,153.3464	$1,153.35	$1,153.35	$1,153.30