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	$91.96	9.672%	$100.8544	$100.85	$100.85	$100.90
Purchase #2	$137.41	6.870%	$146.8501	$146.85	$146.85	$146.90
Purchase #3	$170.27	3.335%	$175.9485	$175.95	$175.95	$175.90
Purchase #4	$173.52	10.249%	$191.3041	$191.30	$191.30	$191.30
Purchase #5	$85.95	3.123%	$88.6342	$88.63	$88.65	$88.60
Purchase #6	$194.60	8.709%	$211.5477	$211.55	$211.55	$211.50
Purchase #7	$199.77	8.744%	$217.2379	$217.24	$217.25	$217.20
7 purchase totals =	$1,053.48		$1,132.3769	$1,132.37	$1,132.40	$1,132.30