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	$107.53	3.341%	$111.1226	$111.12	$111.10	$111.10
Purchase #2	$46.33	13.152%	$52.4233	$52.42	$52.40	$52.40
Purchase #3	$83.66	8.402%	$90.6891	$90.69	$90.70	$90.70
Purchase #4	$200.70	3.357%	$207.4375	$207.44	$207.45	$207.40
Purchase #5	$152.80	7.831%	$164.7658	$164.77	$164.75	$164.80
Purchase #6	$37.40	9.272%	$40.8677	$40.87	$40.85	$40.90
Purchase #7	$24.49	8.252%	$26.5109	$26.51	$26.50	$26.50
7 purchase totals =	$652.91		$693.8169	$693.82	$693.75	$693.80