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	$181.80	6.827%	$194.2115	$194.21	$194.20	$194.20
Purchase #2	$200.54	5.752%	$212.0751	$212.08	$212.10	$212.10
Purchase #3	$209.42	12.808%	$236.2425	$236.24	$236.25	$236.20
Purchase #4	$153.62	5.468%	$162.0199	$162.02	$162.00	$162.00
Purchase #5	$198.57	12.540%	$223.4707	$223.47	$223.45	$223.50
Purchase #6	$94.57	6.504%	$100.7208	$100.72	$100.70	$100.70
Purchase #7	$151.31	3.197%	$156.1474	$156.15	$156.15	$156.10
7 purchase totals =	$1,189.83		$1,284.8879	$1,284.89	$1,284.85	$1,284.80