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	$197.92	3.436%	$204.7205	$204.72	$204.70	$204.70
Purchase #2	$139.86	10.639%	$154.7397	$154.74	$154.75	$154.70
Purchase #3	$223.47	12.314%	$250.9881	$250.99	$251.00	$251.00
Purchase #4	$186.92	7.211%	$200.3988	$200.40	$200.40	$200.40
Purchase #5	$9.33	13.558%	$10.595	$10.60	$10.60	$10.60
Purchase #6	$125.95	12.598%	$141.8172	$141.82	$141.80	$141.80
Purchase #7	$90.80	10.819%	$100.6237	$100.62	$100.60	$100.60
7 purchase totals =	$974.25		$1,063.8830	$1,063.89	$1,063.85	$1,063.80