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	$224.43	6.258%	$238.4748	$238.47	$238.45	$238.50
Purchase #2	$226.86	10.217%	$250.0383	$250.04	$250.05	$250.00
Purchase #3	$178.67	6.551%	$190.3747	$190.37	$190.35	$190.40
Purchase #4	$35.36	7.220%	$37.913	$37.91	$37.90	$37.90
Purchase #5	$218.90	8.731%	$238.0122	$238.01	$238.00	$238.00
Purchase #6	$76.98	7.439%	$82.7065	$82.71	$82.70	$82.70
Purchase #7	$179.66	8.691%	$195.2743	$195.27	$195.25	$195.30
7 purchase totals =	$1,140.86		$1,232.7938	$1,232.78	$1,232.70	$1,232.80