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	$141.64	6.687%	$151.1115	$151.11	$151.10	$151.10
Purchase #2	$116.82	3.720%	$121.1657	$121.17	$121.15	$121.20
Purchase #3	$226.49	12.654%	$255.15	$255.15	$255.15	$255.20
Purchase #4	$164.47	4.746%	$172.2757	$172.28	$172.30	$172.30
Purchase #5	$175.72	12.140%	$197.0524	$197.05	$197.05	$197.10
Purchase #6	$159.85	5.661%	$168.8991	$168.90	$168.90	$168.90
Purchase #7	$147.80	12.659%	$166.51	$166.51	$166.50	$166.50
7 purchase totals =	$1,132.79		$1,232.1644	$1,232.17	$1,232.15	$1,232.30