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	$44.38	6.657%	$47.3344	$47.33	$47.35	$47.30
Purchase #2	$43.80	9.534%	$47.9759	$47.98	$48.00	$48.00
Purchase #3	$83.74	9.644%	$91.8159	$91.82	$91.80	$91.80
Purchase #4	$209.79	8.360%	$227.3284	$227.33	$227.35	$227.30
Purchase #5	$100.69	4.862%	$105.5855	$105.59	$105.60	$105.60
Purchase #6	$64.37	12.325%	$72.3036	$72.30	$72.30	$72.30
Purchase #7	$161.39	11.653%	$180.1968	$180.20	$180.20	$180.20
7 purchase totals =	$708.16		$772.5405	$772.55	$772.60	$772.50