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	$245.92	12.136%	$275.7649	$275.76	$275.75	$275.80
Purchase #2	$222.99	4.481%	$232.9822	$232.98	$233.00	$233.00
Purchase #3	$208.87	6.714%	$222.8935	$222.89	$222.90	$222.90
Purchase #4	$82.27	8.798%	$89.5081	$89.51	$89.50	$89.50
Purchase #5	$110.76	5.609%	$116.9725	$116.97	$116.95	$117.00
Purchase #6	$249.58	10.235%	$275.1245	$275.12	$275.10	$275.10
Purchase #7	$194.38	9.330%	$212.5157	$212.52	$212.50	$212.50
7 purchase totals =	$1,314.77		$1,425.7614	$1,425.75	$1,425.70	$1,425.80