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	$171.78	3.771%	$178.2578	$178.26	$178.25	$178.30
Purchase #2	$127.28	11.574%	$142.0114	$142.01	$142.00	$142.00
Purchase #3	$200.81	10.794%	$222.4854	$222.49	$222.50	$222.50
Purchase #4	$164.90	12.418%	$185.3773	$185.38	$185.40	$185.40
Purchase #5	$43.68	5.199%	$45.9509	$45.95	$45.95	$46.00
Purchase #6	$140.68	7.291%	$150.937	$150.94	$150.95	$150.90
Purchase #7	$246.46	11.650%	$275.1726	$275.17	$275.15	$275.20
7 purchase totals =	$1,095.59		$1,200.1924	$1,200.20	$1,200.20	$1,200.30