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	$240.67	10.317%	$265.4999	$265.50	$265.50	$265.50
Purchase #2	$50.73	9.768%	$55.6853	$55.69	$55.70	$55.70
Purchase #3	$173.60	7.617%	$186.8231	$186.82	$186.80	$186.80
Purchase #4	$213.54	11.829%	$238.7996	$238.80	$238.80	$238.80
Purchase #5	$64.99	11.411%	$72.406	$72.41	$72.40	$72.40
Purchase #6	$34.27	6.816%	$36.6058	$36.61	$36.60	$36.60
Purchase #7	$156.47	12.298%	$175.7127	$175.71	$175.70	$175.70
7 purchase totals =	$934.27		$1,031.5324	$1,031.54	$1,031.50	$1,031.50