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	$80.53	7.753%	$86.7735	$86.77	$86.75	$86.80
Purchase #2	$189.31	10.480%	$209.1497	$209.15	$209.15	$209.10
Purchase #3	$223.60	12.194%	$250.8658	$250.87	$250.85	$250.90
Purchase #4	$216.44	7.713%	$233.134	$233.13	$233.15	$233.10
Purchase #5	$18.95	8.165%	$20.4973	$20.50	$20.50	$20.50
Purchase #6	$44.95	3.767%	$46.6433	$46.64	$46.65	$46.60
Purchase #7	$189.67	9.760%	$208.1818	$208.18	$208.20	$208.20
7 purchase totals =	$963.45		$1,055.2454	$1,055.24	$1,055.25	$1,055.20