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	$153.71	9.496%	$168.3063	$168.31	$168.30	$168.30
Purchase #2	$147.98	3.701%	$153.4567	$153.46	$153.45	$153.50
Purchase #3	$176.68	10.724%	$195.6272	$195.63	$195.65	$195.60
Purchase #4	$53.88	10.230%	$59.3919	$59.39	$59.40	$59.40
Purchase #5	$145.71	13.384%	$165.2118	$165.21	$165.20	$165.20
Purchase #6	$51.88	13.778%	$59.028	$59.03	$59.05	$59.00
Purchase #7	$91.57	11.691%	$102.2754	$102.28	$102.30	$102.30
7 purchase totals =	$821.41		$903.2973	$903.31	$903.35	$903.30