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	$190.43	13.157%	$215.4849	$215.48	$215.50	$215.50
Purchase #2	$196.95	13.546%	$223.6288	$223.63	$223.65	$223.60
Purchase #3	$132.46	3.288%	$136.8153	$136.82	$136.80	$136.80
Purchase #4	$113.97	3.417%	$117.8644	$117.86	$117.85	$117.90
Purchase #5	$234.39	5.173%	$246.515	$246.52	$246.50	$246.50
Purchase #6	$105.67	5.817%	$111.8168	$111.82	$111.80	$111.80
Purchase #7	$81.58	10.312%	$89.9925	$89.99	$90.00	$90.00
7 purchase totals =	$1,055.45		$1,142.1177	$1,142.12	$1,142.10	$1,142.10