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	$67.51	12.505%	$75.9521	$75.95	$75.95	$76.00
Purchase #2	$169.27	10.566%	$187.1551	$187.16	$187.15	$187.20
Purchase #3	$145.85	4.750%	$152.7779	$152.78	$152.80	$152.80
Purchase #4	$82.79	9.594%	$90.7329	$90.73	$90.75	$90.70
Purchase #5	$135.93	7.413%	$146.0065	$146.01	$146.00	$146.00
Purchase #6	$68.55	8.314%	$74.2492	$74.25	$74.25	$74.20
Purchase #7	$175.45	12.184%	$196.8268	$196.83	$196.85	$196.80
7 purchase totals =	$845.35		$923.7005	$923.71	$923.75	$923.70