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	$221.93	4.428%	$231.7571	$231.76	$231.75	$231.80
Purchase #2	$121.64	7.332%	$130.5586	$130.56	$130.55	$130.60
Purchase #3	$86.27	4.282%	$89.9641	$89.96	$89.95	$90.00
Purchase #4	$196.49	13.427%	$222.8727	$222.87	$222.85	$222.90
Purchase #5	$19.50	4.394%	$20.3568	$20.36	$20.35	$20.40
Purchase #6	$7.49	8.491%	$8.126	$8.13	$8.15	$8.10
Purchase #7	$35.33	6.176%	$37.512	$37.51	$37.50	$37.50
7 purchase totals =	$688.65		$741.1473	$741.15	$741.10	$741.30