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	$41.62	6.130%	$44.1713	$44.17	$44.15	$44.20
Purchase #2	$146.75	12.459%	$165.0336	$165.03	$165.05	$165.00
Purchase #3	$142.28	13.509%	$161.5006	$161.50	$161.50	$161.50
Purchase #4	$85.55	12.148%	$95.9426	$95.94	$95.95	$95.90
Purchase #5	$107.88	9.274%	$117.8848	$117.88	$117.90	$117.90
Purchase #6	$105.82	10.107%	$116.5152	$116.52	$116.50	$116.50
Purchase #7	$158.83	8.157%	$171.7858	$171.79	$171.80	$171.80
7 purchase totals =	$788.73		$872.8339	$872.83	$872.85	$872.80