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	$130.41	13.340%	$147.8067	$147.81	$147.80	$147.80
Purchase #2	$140.87	3.540%	$145.8568	$145.86	$145.85	$145.90
Purchase #3	$202.39	10.412%	$223.4628	$223.46	$223.45	$223.50
Purchase #4	$80.39	10.798%	$89.0705	$89.07	$89.05	$89.10
Purchase #5	$27.99	13.800%	$31.8526	$31.85	$31.85	$31.90
Purchase #6	$152.48	11.851%	$170.5504	$170.55	$170.55	$170.60
Purchase #7	$148.38	3.472%	$153.5318	$153.53	$153.55	$153.50
7 purchase totals =	$882.91		$962.1316	$962.13	$962.10	$962.30