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	$139.58	5.258%	$146.9191	$146.92	$146.90	$146.90
Purchase #2	$209.35	13.728%	$238.0896	$238.09	$238.10	$238.10
Purchase #3	$7.48	4.466%	$7.8141	$7.81	$7.80	$7.80
Purchase #4	$246.51	7.149%	$264.133	$264.13	$264.15	$264.10
Purchase #5	$51.42	6.782%	$54.9073	$54.91	$54.90	$54.90
Purchase #6	$201.67	12.146%	$226.1648	$226.16	$226.15	$226.20
Purchase #7	$136.83	11.677%	$152.8076	$152.81	$152.80	$152.80
7 purchase totals =	$992.84		$1,090.8355	$1,090.83	$1,090.80	$1,090.80