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	$174.85	9.653%	$191.7283	$191.73	$191.75	$191.70
Purchase #2	$27.43	7.867%	$29.5879	$29.59	$29.60	$29.60
Purchase #3	$241.47	4.171%	$251.5417	$251.54	$251.55	$251.50
Purchase #4	$238.79	6.231%	$253.669	$253.67	$253.65	$253.70
Purchase #5	$228.87	11.470%	$255.1214	$255.12	$255.10	$255.10
Purchase #6	$198.31	13.826%	$225.7283	$225.73	$225.75	$225.70
Purchase #7	$43.89	8.223%	$47.4991	$47.50	$47.50	$47.50
7 purchase totals =	$1,153.61		$1,254.8757	$1,254.88	$1,254.90	$1,254.80