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	$141.83	7.386%	$152.3056	$152.31	$152.30	$152.30
Purchase #2	$204.95	8.431%	$222.2293	$222.23	$222.25	$222.20
Purchase #3	$198.28	9.724%	$217.5607	$217.56	$217.55	$217.60
Purchase #4	$232.42	12.439%	$261.3307	$261.33	$261.35	$261.30
Purchase #5	$35.92	3.219%	$37.0763	$37.08	$37.10	$37.10
Purchase #6	$81.61	13.439%	$92.5776	$92.58	$92.60	$92.60
Purchase #7	$151.67	10.739%	$167.9578	$167.96	$167.95	$168.00
7 purchase totals =	$1,046.68		$1,151.0380	$1,151.05	$1,151.10	$1,151.10