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	$139.38	13.853%	$158.6883	$158.69	$158.70	$158.70
Purchase #2	$222.61	10.735%	$246.5072	$246.51	$246.50	$246.50
Purchase #3	$90.71	4.290%	$94.6015	$94.60	$94.60	$94.60
Purchase #4	$32.56	13.321%	$36.8973	$36.90	$36.90	$36.90
Purchase #5	$159.78	3.544%	$165.4426	$165.44	$165.45	$165.40
Purchase #6	$201.55	3.392%	$208.3866	$208.39	$208.40	$208.40
Purchase #7	$95.80	10.672%	$106.0238	$106.02	$106.00	$106.00
7 purchase totals =	$942.39		$1,016.5473	$1,016.55	$1,016.55	$1,016.50