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	$90.51	4.359%	$94.4553	$94.46	$94.45	$94.50
Purchase #2	$120.98	13.702%	$137.5567	$137.56	$137.55	$137.60
Purchase #3	$121.91	7.268%	$130.7704	$130.77	$130.75	$130.80
Purchase #4	$58.54	4.617%	$61.2428	$61.24	$61.25	$61.20
Purchase #5	$233.59	6.338%	$248.3949	$248.39	$248.40	$248.40
Purchase #6	$163.67	13.388%	$185.5821	$185.58	$185.60	$185.60
Purchase #7	$99.49	4.167%	$103.6357	$103.64	$103.65	$103.60
7 purchase totals =	$888.69		$961.6379	$961.64	$961.65	$961.70