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	$119.37	9.505%	$130.7161	$130.72	$130.70	$130.70
Purchase #2	$218.58	9.496%	$239.3364	$239.34	$239.35	$239.30
Purchase #3	$99.79	5.667%	$105.4451	$105.45	$105.45	$105.40
Purchase #4	$61.31	13.245%	$69.4305	$69.43	$69.45	$69.40
Purchase #5	$161.76	7.257%	$173.4989	$173.50	$173.50	$173.50
Purchase #6	$90.48	13.369%	$102.5763	$102.58	$102.60	$102.60
Purchase #7	$167.43	10.377%	$184.8042	$184.80	$184.80	$184.80
7 purchase totals =	$918.72		$1,005.8075	$1,005.82	$1,005.85	$1,005.70