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	$198.54	5.197%	$208.8581	$208.86	$208.85	$208.90
Purchase #2	$175.61	8.491%	$190.521	$190.52	$190.50	$190.50
Purchase #3	$42.69	9.204%	$46.6192	$46.62	$46.60	$46.60
Purchase #4	$80.86	13.375%	$91.675	$91.68	$91.70	$91.70
Purchase #5	$200.30	4.711%	$209.7361	$209.74	$209.75	$209.70
Purchase #6	$61.70	4.184%	$64.2815	$64.28	$64.30	$64.30
Purchase #7	$101.87	9.835%	$111.8889	$111.89	$111.90	$111.90
7 purchase totals =	$861.57		$923.5798	$923.59	$923.60	$923.60