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	$202.44	3.490%	$209.5052	$209.51	$209.50	$209.50
Purchase #2	$131.29	12.476%	$147.6697	$147.67	$147.65	$147.70
Purchase #3	$84.94	7.181%	$91.0395	$91.04	$91.05	$91.00
Purchase #4	$244.70	13.143%	$276.8609	$276.86	$276.85	$276.90
Purchase #5	$82.86	9.290%	$90.5577	$90.56	$90.55	$90.60
Purchase #6	$84.85	13.661%	$96.4414	$96.44	$96.45	$96.40
Purchase #7	$34.77	10.667%	$38.4789	$38.48	$38.50	$38.50
7 purchase totals =	$865.85		$950.5533	$950.56	$950.55	$950.60