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	$61.37	7.825%	$66.1722	$66.17	$66.15	$66.20
Purchase #2	$148.48	11.290%	$165.2434	$165.24	$165.25	$165.20
Purchase #3	$96.49	6.162%	$102.4357	$102.44	$102.45	$102.40
Purchase #4	$216.29	10.540%	$239.087	$239.09	$239.10	$239.10
Purchase #5	$241.64	3.787%	$250.7909	$250.79	$250.80	$250.80
Purchase #6	$95.79	4.274%	$99.8841	$99.88	$99.90	$99.90
Purchase #7	$180.58	10.678%	$199.8623	$199.86	$199.85	$199.90
7 purchase totals =	$1,040.64		$1,123.4756	$1,123.47	$1,123.50	$1,123.50