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	$191.49	12.332%	$215.1045	$215.10	$215.10	$215.10
Purchase #2	$164.57	9.867%	$180.8081	$180.81	$180.80	$180.80
Purchase #3	$134.62	3.788%	$139.7194	$139.72	$139.70	$139.70
Purchase #4	$36.77	3.249%	$37.9647	$37.96	$37.95	$38.00
Purchase #5	$151.89	13.400%	$172.2433	$172.24	$172.25	$172.20
Purchase #6	$179.27	10.418%	$197.9463	$197.95	$197.95	$197.90
Purchase #7	$82.46	10.259%	$90.9196	$90.92	$90.90	$90.90
7 purchase totals =	$941.07		$1,034.7059	$1,034.70	$1,034.65	$1,034.60