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	$89.35	6.771%	$95.3999	$95.40	$95.40	$95.40
Purchase #2	$185.45	13.489%	$210.4654	$210.47	$210.45	$210.50
Purchase #3	$15.72	9.600%	$17.2291	$17.23	$17.25	$17.20
Purchase #4	$207.57	7.173%	$222.459	$222.46	$222.45	$222.50
Purchase #5	$142.96	10.491%	$157.9579	$157.96	$157.95	$158.00
Purchase #6	$135.51	5.340%	$142.7462	$142.75	$142.75	$142.70
Purchase #7	$223.50	3.747%	$231.8745	$231.87	$231.85	$231.90
7 purchase totals =	$1,000.06		$1,078.1320	$1,078.14	$1,078.10	$1,078.20