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	$193.65	10.635%	$214.2447	$214.24	$214.25	$214.20
Purchase #2	$150.54	3.279%	$155.4762	$155.48	$155.50	$155.50
Purchase #3	$178.40	6.853%	$190.6258	$190.63	$190.65	$190.60
Purchase #4	$82.66	9.671%	$90.654	$90.65	$90.65	$90.70
Purchase #5	$18.37	9.123%	$20.0459	$20.05	$20.05	$20.00
Purchase #6	$231.57	7.296%	$248.4653	$248.47	$248.45	$248.50
Purchase #7	$50.36	9.503%	$55.1457	$55.15	$55.15	$55.10
7 purchase totals =	$905.55		$974.6576	$974.67	$974.70	$974.60