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	$203.72	9.269%	$222.6028	$222.60	$222.60	$222.60
Purchase #2	$138.26	10.162%	$152.31	$152.31	$152.30	$152.30
Purchase #3	$147.62	6.165%	$156.7208	$156.72	$156.70	$156.70
Purchase #4	$158.77	11.523%	$177.0651	$177.07	$177.05	$177.10
Purchase #5	$91.34	12.615%	$102.8625	$102.86	$102.85	$102.90
Purchase #6	$47.72	3.636%	$49.4551	$49.46	$49.45	$49.50
Purchase #7	$138.31	6.679%	$147.5477	$147.55	$147.55	$147.50
7 purchase totals =	$925.74		$1,008.5640	$1,008.57	$1,008.50	$1,008.60