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	$203.59	11.619%	$227.2451	$227.25	$227.25	$227.20
Purchase #2	$27.73	4.841%	$29.0724	$29.07	$29.05	$29.10
Purchase #3	$184.58	6.447%	$196.4799	$196.48	$196.50	$196.50
Purchase #4	$196.32	10.187%	$216.3191	$216.32	$216.30	$216.30
Purchase #5	$126.26	10.301%	$139.266	$139.27	$139.25	$139.30
Purchase #6	$86.37	6.275%	$91.7897	$91.79	$91.80	$91.80
Purchase #7	$137.42	7.420%	$147.6166	$147.62	$147.60	$147.60
7 purchase totals =	$962.27		$1,047.7888	$1,047.80	$1,047.75	$1,047.80