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	$218.52	6.498%	$232.7194	$232.72	$232.70	$232.70
Purchase #2	$157.40	10.260%	$173.5492	$173.55	$173.55	$173.50
Purchase #3	$6.61	10.776%	$7.3223	$7.32	$7.30	$7.30
Purchase #4	$52.90	8.379%	$57.3325	$57.33	$57.35	$57.30
Purchase #5	$114.67	7.436%	$123.1969	$123.20	$123.20	$123.20
Purchase #6	$83.85	12.611%	$94.4243	$94.42	$94.40	$94.40
Purchase #7	$128.66	13.849%	$146.4781	$146.48	$146.50	$146.50
7 purchase totals =	$762.61		$835.0227	$835.02	$835.00	$834.90