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	$166.44	13.395%	$188.7346	$188.73	$188.75	$188.70
Purchase #2	$180.28	7.367%	$193.5612	$193.56	$193.55	$193.60
Purchase #3	$57.41	4.369%	$59.9182	$59.92	$59.90	$59.90
Purchase #4	$20.50	13.562%	$23.2802	$23.28	$23.30	$23.30
Purchase #5	$175.45	5.824%	$185.6682	$185.67	$185.65	$185.70
Purchase #6	$52.92	12.296%	$59.427	$59.43	$59.45	$59.40
Purchase #7	$205.43	7.562%	$220.9646	$220.96	$220.95	$221.00
7 purchase totals =	$858.43		$931.5540	$931.55	$931.55	$931.60