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	$106.88	8.333%	$115.7863	$115.79	$115.80	$115.80
Purchase #2	$89.50	8.838%	$97.41	$97.41	$97.40	$97.40
Purchase #3	$225.82	13.137%	$255.486	$255.49	$255.50	$255.50
Purchase #4	$57.46	3.850%	$59.6722	$59.67	$59.65	$59.70
Purchase #5	$169.30	11.589%	$188.9202	$188.92	$188.90	$188.90
Purchase #6	$50.89	12.569%	$57.2864	$57.29	$57.30	$57.30
Purchase #7	$242.76	6.660%	$258.9278	$258.93	$258.95	$258.90
7 purchase totals =	$942.61		$1,033.4889	$1,033.50	$1,033.50	$1,033.50