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	$73.45	6.487%	$78.2147	$78.21	$78.20	$78.20
Purchase #2	$66.43	11.245%	$73.9001	$73.90	$73.90	$73.90
Purchase #3	$86.66	12.197%	$97.2299	$97.23	$97.25	$97.20
Purchase #4	$6.36	12.611%	$7.1621	$7.16	$7.15	$7.20
Purchase #5	$50.93	6.229%	$54.1024	$54.10	$54.10	$54.10
Purchase #6	$65.91	9.347%	$72.0706	$72.07	$72.05	$72.10
Purchase #7	$11.86	12.484%	$13.3406	$13.34	$13.35	$13.30
7 purchase totals =	$361.60		$396.0204	$396.01	$396.00	$396.00