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	$121.56	8.690%	$132.1236	$132.12	$132.10	$132.10
Purchase #2	$180.82	10.635%	$200.0502	$200.05	$200.05	$200.10
Purchase #3	$77.94	5.829%	$82.4831	$82.48	$82.50	$82.50
Purchase #4	$78.25	8.311%	$84.7534	$84.75	$84.75	$84.80
Purchase #5	$28.85	12.547%	$32.4698	$32.47	$32.45	$32.50
Purchase #6	$24.30	4.850%	$25.4786	$25.48	$25.50	$25.50
Purchase #7	$127.44	10.349%	$140.6288	$140.63	$140.65	$140.60
7 purchase totals =	$639.16		$697.9875	$697.98	$698.00	$698.10