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	$212.77	7.776%	$229.315	$229.32	$229.30	$229.30
Purchase #2	$227.59	8.710%	$247.4131	$247.41	$247.40	$247.40
Purchase #3	$33.40	11.835%	$37.3529	$37.35	$37.35	$37.40
Purchase #4	$118.50	9.787%	$130.0976	$130.10	$130.10	$130.10
Purchase #5	$238.53	8.459%	$258.7073	$258.71	$258.70	$258.70
Purchase #6	$100.98	11.339%	$112.4301	$112.43	$112.45	$112.40
Purchase #7	$109.84	5.769%	$116.1767	$116.18	$116.20	$116.20
7 purchase totals =	$1,041.61		$1,131.4927	$1,131.50	$1,131.50	$1,131.50