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	$77.80	11.745%	$86.9376	$86.94	$86.95	$86.90
Purchase #2	$222.82	11.468%	$248.373	$248.37	$248.35	$248.40
Purchase #3	$77.50	4.683%	$81.1293	$81.13	$81.15	$81.10
Purchase #4	$210.77	9.487%	$230.7657	$230.77	$230.75	$230.80
Purchase #5	$231.75	5.508%	$244.5148	$244.51	$244.50	$244.50
Purchase #6	$54.88	8.172%	$59.3648	$59.36	$59.35	$59.40
Purchase #7	$161.59	11.438%	$180.0727	$180.07	$180.05	$180.10
7 purchase totals =	$1,037.11		$1,131.1579	$1,131.15	$1,131.10	$1,131.20