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	$155.57	4.555%	$162.6562	$162.66	$162.65	$162.70
Purchase #2	$227.68	12.213%	$255.4866	$255.49	$255.50	$255.50
Purchase #3	$233.31	9.702%	$255.9457	$255.95	$255.95	$255.90
Purchase #4	$57.74	5.226%	$60.7575	$60.76	$60.75	$60.80
Purchase #5	$198.61	8.327%	$215.1483	$215.15	$215.15	$215.10
Purchase #6	$32.52	11.444%	$36.2416	$36.24	$36.25	$36.20
Purchase #7	$57.40	12.768%	$64.7288	$64.73	$64.75	$64.70
7 purchase totals =	$962.83		$1,050.9647	$1,050.98	$1,051.00	$1,050.90