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	$194.96	9.558%	$213.5943	$213.59	$213.60	$213.60
Purchase #2	$250.98	13.143%	$283.9663	$283.97	$283.95	$284.00
Purchase #3	$73.64	11.552%	$82.1469	$82.15	$82.15	$82.10
Purchase #4	$40.33	6.487%	$42.9462	$42.95	$42.95	$42.90
Purchase #5	$247.31	12.169%	$277.4052	$277.41	$277.40	$277.40
Purchase #6	$143.56	11.150%	$159.5669	$159.57	$159.55	$159.60
Purchase #7	$171.59	4.626%	$179.5278	$179.53	$179.55	$179.50
7 purchase totals =	$1,122.37		$1,239.1536	$1,239.17	$1,239.15	$1,239.10