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	$203.97	4.647%	$213.4485	$213.45	$213.45	$213.40
Purchase #2	$60.57	7.210%	$64.9371	$64.94	$64.95	$64.90
Purchase #3	$140.38	8.450%	$152.2421	$152.24	$152.25	$152.20
Purchase #4	$48.52	8.115%	$52.4574	$52.46	$52.45	$52.50
Purchase #5	$73.89	8.824%	$80.4101	$80.41	$80.40	$80.40
Purchase #6	$130.59	10.722%	$144.5919	$144.59	$144.60	$144.60
Purchase #7	$21.91	7.281%	$23.5053	$23.51	$23.50	$23.50
7 purchase totals =	$679.83		$731.5924	$731.60	$731.60	$731.50