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	$28.25	13.310%	$32.0101	$32.01	$32.00	$32.00
Purchase #2	$34.46	8.221%	$37.293	$37.29	$37.30	$37.30
Purchase #3	$29.64	13.683%	$33.6956	$33.70	$33.70	$33.70
Purchase #4	$167.89	10.531%	$185.5705	$185.57	$185.55	$185.60
Purchase #5	$76.60	4.847%	$80.3128	$80.31	$80.30	$80.30
Purchase #6	$65.65	6.839%	$70.1398	$70.14	$70.15	$70.10
Purchase #7	$236.72	11.342%	$263.5688	$263.57	$263.55	$263.60
7 purchase totals =	$639.21		$702.5906	$702.59	$702.55	$702.60