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	$73.50	10.853%	$81.477	$81.48	$81.50	$81.50
Purchase #2	$191.81	9.412%	$209.8632	$209.86	$209.85	$209.90
Purchase #3	$73.35	9.691%	$80.4583	$80.46	$80.45	$80.50
Purchase #4	$240.70	5.113%	$253.007	$253.01	$253.00	$253.00
Purchase #5	$64.50	12.364%	$72.4748	$72.47	$72.45	$72.50
Purchase #6	$152.80	3.567%	$158.2504	$158.25	$158.25	$158.30
Purchase #7	$10.32	10.367%	$11.3899	$11.39	$11.40	$11.40
7 purchase totals =	$806.98		$866.9206	$866.92	$866.90	$867.10