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	$114.85	7.517%	$123.4833	$123.48	$123.50	$123.50
Purchase #2	$191.66	13.316%	$217.1814	$217.18	$217.20	$217.20
Purchase #3	$40.87	12.870%	$46.13	$46.13	$46.15	$46.10
Purchase #4	$165.55	6.441%	$176.2131	$176.21	$176.20	$176.20
Purchase #5	$99.95	8.480%	$108.4258	$108.43	$108.45	$108.40
Purchase #6	$116.96	6.527%	$124.594	$124.59	$124.60	$124.60
Purchase #7	$243.48	8.145%	$263.3114	$263.31	$263.30	$263.30
7 purchase totals =	$973.32		$1,059.3390	$1,059.33	$1,059.40	$1,059.30