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	$59.32	10.248%	$65.3991	$65.40	$65.40	$65.40
Purchase #2	$177.51	7.700%	$191.1783	$191.18	$191.20	$191.20
Purchase #3	$29.40	7.322%	$31.5527	$31.55	$31.55	$31.60
Purchase #4	$187.78	11.842%	$210.0169	$210.02	$210.00	$210.00
Purchase #5	$213.35	13.657%	$242.4872	$242.49	$242.50	$242.50
Purchase #6	$37.95	7.866%	$40.9351	$40.94	$40.95	$40.90
Purchase #7	$185.87	5.774%	$196.6021	$196.60	$196.60	$196.60
7 purchase totals =	$891.18		$978.1714	$978.18	$978.20	$978.20