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	$241.73	4.121%	$251.6917	$251.69	$251.70	$251.70
Purchase #2	$27.66	3.433%	$28.6096	$28.61	$28.60	$28.60
Purchase #3	$36.80	7.252%	$39.4687	$39.47	$39.45	$39.50
Purchase #4	$35.82	7.357%	$38.4553	$38.46	$38.45	$38.50
Purchase #5	$239.39	10.383%	$264.2459	$264.25	$264.25	$264.20
Purchase #6	$190.88	8.248%	$206.6238	$206.62	$206.60	$206.60
Purchase #7	$59.54	13.160%	$67.3755	$67.38	$67.40	$67.40
7 purchase totals =	$831.82		$896.4705	$896.48	$896.45	$896.50