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	$154.26	6.554%	$164.3702	$164.37	$164.35	$164.40
Purchase #2	$90.74	12.451%	$102.038	$102.04	$102.05	$102.00
Purchase #3	$213.80	11.375%	$238.1198	$238.12	$238.10	$238.10
Purchase #4	$31.83	6.411%	$33.8706	$33.87	$33.85	$33.90
Purchase #5	$146.93	3.438%	$151.9815	$151.98	$152.00	$152.00
Purchase #6	$187.48	11.327%	$208.7159	$208.72	$208.70	$208.70
Purchase #7	$235.45	4.483%	$246.0052	$246.01	$246.00	$246.00
7 purchase totals =	$1,060.49		$1,145.1012	$1,145.11	$1,145.05	$1,145.10