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	$202.51	3.776%	$210.1568	$210.16	$210.15	$210.20
Purchase #2	$98.63	7.325%	$105.8546	$105.85	$105.85	$105.90
Purchase #3	$54.36	10.239%	$59.9259	$59.93	$59.95	$59.90
Purchase #4	$52.32	11.490%	$58.3316	$58.33	$58.35	$58.30
Purchase #5	$68.77	10.826%	$76.215	$76.22	$76.20	$76.20
Purchase #6	$202.71	11.292%	$225.6	$225.60	$225.60	$225.60
Purchase #7	$58.55	3.199%	$60.423	$60.42	$60.40	$60.40
7 purchase totals =	$737.85		$796.5069	$796.51	$796.50	$796.50