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	$61.69	10.716%	$68.3007	$68.30	$68.30	$68.30
Purchase #2	$152.30	6.385%	$162.0244	$162.02	$162.00	$162.00
Purchase #3	$89.59	13.446%	$101.6363	$101.64	$101.65	$101.60
Purchase #4	$234.59	6.267%	$249.2918	$249.29	$249.30	$249.30
Purchase #5	$179.67	5.846%	$190.1735	$190.17	$190.15	$190.20
Purchase #6	$231.94	10.297%	$255.8229	$255.82	$255.80	$255.80
Purchase #7	$230.79	13.742%	$262.5052	$262.51	$262.50	$262.50
7 purchase totals =	$1,180.57		$1,289.7548	$1,289.75	$1,289.70	$1,289.70