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	$207.74	9.260%	$226.9767	$226.98	$227.00	$227.00
Purchase #2	$36.74	7.223%	$39.3937	$39.39	$39.40	$39.40
Purchase #3	$34.93	6.576%	$37.227	$37.23	$37.25	$37.20
Purchase #4	$107.72	12.390%	$121.0665	$121.07	$121.05	$121.10
Purchase #5	$10.27	12.179%	$11.5208	$11.52	$11.50	$11.50
Purchase #6	$78.75	4.602%	$82.3741	$82.37	$82.35	$82.40
Purchase #7	$224.32	8.723%	$243.8874	$243.89	$243.90	$243.90
7 purchase totals =	$700.47		$762.4462	$762.45	$762.45	$762.50