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	$75.48	13.228%	$85.4645	$85.46	$85.45	$85.50
Purchase #2	$195.38	13.721%	$222.1881	$222.19	$222.20	$222.20
Purchase #3	$112.41	7.698%	$121.0633	$121.06	$121.05	$121.10
Purchase #4	$188.66	8.659%	$204.9961	$205.00	$205.00	$205.00
Purchase #5	$203.54	9.179%	$222.2229	$222.22	$222.20	$222.20
Purchase #6	$103.44	10.742%	$114.5515	$114.55	$114.55	$114.60
Purchase #7	$111.55	4.190%	$116.2239	$116.22	$116.20	$116.20
7 purchase totals =	$990.46		$1,086.7103	$1,086.70	$1,086.65	$1,086.80