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	$228.73	10.853%	$253.5541	$253.55	$253.55	$253.60
Purchase #2	$86.42	3.632%	$89.5588	$89.56	$89.55	$89.60
Purchase #3	$52.81	12.606%	$59.4672	$59.47	$59.45	$59.50
Purchase #4	$183.31	8.865%	$199.5604	$199.56	$199.55	$199.60
Purchase #5	$246.52	3.644%	$255.5032	$255.50	$255.50	$255.50
Purchase #6	$228.65	7.505%	$245.8102	$245.81	$245.80	$245.80
Purchase #7	$40.87	5.609%	$43.1624	$43.16	$43.15	$43.20
7 purchase totals =	$1,067.31		$1,146.6163	$1,146.61	$1,146.55	$1,146.80