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	$44.46	3.167%	$45.868	$45.87	$45.85	$45.90
Purchase #2	$247.65	12.857%	$279.4904	$279.49	$279.50	$279.50
Purchase #3	$47.56	4.150%	$49.5337	$49.53	$49.55	$49.50
Purchase #4	$94.39	10.589%	$104.385	$104.39	$104.40	$104.40
Purchase #5	$142.37	9.637%	$156.0902	$156.09	$156.10	$156.10
Purchase #6	$164.58	4.851%	$172.5638	$172.56	$172.55	$172.60
Purchase #7	$200.41	8.383%	$217.2104	$217.21	$217.20	$217.20
7 purchase totals =	$941.42		$1,025.1415	$1,025.14	$1,025.15	$1,025.20