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	$146.89	13.754%	$167.0933	$167.09	$167.10	$167.10
Purchase #2	$111.42	4.654%	$116.6055	$116.61	$116.60	$116.60
Purchase #3	$201.81	11.441%	$224.8991	$224.90	$224.90	$224.90
Purchase #4	$221.39	9.739%	$242.9512	$242.95	$242.95	$243.00
Purchase #5	$59.76	8.281%	$64.7087	$64.71	$64.70	$64.70
Purchase #6	$113.42	4.519%	$118.5454	$118.55	$118.55	$118.50
Purchase #7	$123.79	3.429%	$128.0348	$128.03	$128.05	$128.00
7 purchase totals =	$978.48		$1,062.8380	$1,062.84	$1,062.85	$1,062.80