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	$205.30	7.760%	$221.2313	$221.23	$221.25	$221.20
Purchase #2	$90.89	4.398%	$94.8873	$94.89	$94.90	$94.90
Purchase #3	$95.60	12.367%	$107.4229	$107.42	$107.40	$107.40
Purchase #4	$124.28	10.789%	$137.6886	$137.69	$137.70	$137.70
Purchase #5	$191.36	13.403%	$217.008	$217.01	$217.00	$217.00
Purchase #6	$72.40	6.331%	$76.9836	$76.98	$77.00	$77.00
Purchase #7	$56.45	5.591%	$59.6061	$59.61	$59.60	$59.60
7 purchase totals =	$836.28		$914.8278	$914.83	$914.85	$914.80