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	$87.62	10.388%	$96.722	$96.72	$96.70	$96.70
Purchase #2	$102.62	8.806%	$111.6567	$111.66	$111.65	$111.70
Purchase #3	$109.77	6.478%	$116.8809	$116.88	$116.90	$116.90
Purchase #4	$92.69	12.556%	$104.3282	$104.33	$104.35	$104.30
Purchase #5	$44.38	3.344%	$45.8641	$45.86	$45.85	$45.90
Purchase #6	$18.86	8.152%	$20.3975	$20.40	$20.40	$20.40
Purchase #7	$97.31	5.715%	$102.8713	$102.87	$102.85	$102.90
7 purchase totals =	$553.25		$598.7207	$598.72	$598.70	$598.80