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	$62.79	12.245%	$70.4786	$70.48	$70.50	$70.50
Purchase #2	$115.96	3.569%	$120.0986	$120.10	$120.10	$120.10
Purchase #3	$178.65	8.650%	$194.1032	$194.10	$194.10	$194.10
Purchase #4	$28.31	13.706%	$32.1902	$32.19	$32.20	$32.20
Purchase #5	$178.58	12.198%	$200.3632	$200.36	$200.35	$200.40
Purchase #6	$59.69	9.874%	$65.5838	$65.58	$65.60	$65.60
Purchase #7	$15.88	13.398%	$18.0076	$18.01	$18.00	$18.00
7 purchase totals =	$639.86		$700.8252	$700.82	$700.85	$700.90