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	$108.78	12.104%	$121.9467	$121.95	$121.95	$121.90
Purchase #2	$39.42	6.411%	$41.9472	$41.95	$41.95	$41.90
Purchase #3	$93.46	7.719%	$100.6742	$100.67	$100.65	$100.70
Purchase #4	$89.50	10.762%	$99.132	$99.13	$99.15	$99.10
Purchase #5	$225.71	13.377%	$255.9032	$255.90	$255.90	$255.90
Purchase #6	$232.66	12.322%	$261.3284	$261.33	$261.35	$261.30
Purchase #7	$212.65	3.287%	$219.6398	$219.64	$219.65	$219.60
7 purchase totals =	$1,002.18		$1,100.5715	$1,100.57	$1,100.60	$1,100.40