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	$83.90	8.290%	$90.8553	$90.86	$90.85	$90.90
Purchase #2	$133.52	3.471%	$138.1545	$138.15	$138.15	$138.20
Purchase #3	$137.41	6.587%	$146.4612	$146.46	$146.45	$146.50
Purchase #4	$138.27	7.465%	$148.5919	$148.59	$148.60	$148.60
Purchase #5	$87.64	12.417%	$98.5223	$98.52	$98.50	$98.50
Purchase #6	$223.46	8.627%	$242.7379	$242.74	$242.75	$242.70
Purchase #7	$154.52	11.588%	$172.4258	$172.43	$172.45	$172.40
7 purchase totals =	$958.72		$1,037.7489	$1,037.75	$1,037.75	$1,037.80