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	$199.63	4.248%	$208.1103	$208.11	$208.10	$208.10
Purchase #2	$246.36	6.136%	$261.4766	$261.48	$261.50	$261.50
Purchase #3	$47.34	13.212%	$53.5946	$53.59	$53.60	$53.60
Purchase #4	$30.28	6.799%	$32.3387	$32.34	$32.35	$32.30
Purchase #5	$94.34	6.333%	$100.3146	$100.31	$100.30	$100.30
Purchase #6	$31.42	5.478%	$33.1412	$33.14	$33.15	$33.10
Purchase #7	$117.79	6.553%	$125.5088	$125.51	$125.50	$125.50
7 purchase totals =	$767.16		$814.4848	$814.48	$814.50	$814.40