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	$200.89	10.871%	$222.7288	$222.73	$222.75	$222.70
Purchase #2	$150.25	10.701%	$166.3283	$166.33	$166.35	$166.30
Purchase #3	$206.83	10.669%	$228.8967	$228.90	$228.90	$228.90
Purchase #4	$100.52	11.389%	$111.9682	$111.97	$111.95	$112.00
Purchase #5	$82.65	8.198%	$89.4256	$89.43	$89.45	$89.40
Purchase #6	$50.59	5.155%	$53.1979	$53.20	$53.20	$53.20
Purchase #7	$201.87	6.846%	$215.69	$215.69	$215.70	$215.70
7 purchase totals =	$993.60		$1,088.2355	$1,088.25	$1,088.30	$1,088.20