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	$127.52	4.637%	$133.4331	$133.43	$133.45	$133.40
Purchase #2	$141.62	3.396%	$146.4294	$146.43	$146.45	$146.40
Purchase #3	$63.31	9.438%	$69.2852	$69.29	$69.30	$69.30
Purchase #4	$101.58	10.198%	$111.9391	$111.94	$111.95	$111.90
Purchase #5	$196.55	7.575%	$211.4387	$211.44	$211.45	$211.40
Purchase #6	$246.53	4.849%	$258.4842	$258.48	$258.50	$258.50
Purchase #7	$89.42	12.709%	$100.7844	$100.78	$100.80	$100.80
7 purchase totals =	$966.53		$1,031.7941	$1,031.79	$1,031.90	$1,031.70