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	$223.35	9.190%	$243.8759	$243.88	$243.90	$243.90
Purchase #2	$69.52	12.470%	$78.1891	$78.19	$78.20	$78.20
Purchase #3	$246.27	8.763%	$267.8506	$267.85	$267.85	$267.90
Purchase #4	$109.43	7.852%	$118.0224	$118.02	$118.00	$118.00
Purchase #5	$75.25	10.800%	$83.377	$83.38	$83.40	$83.40
Purchase #6	$203.95	4.710%	$213.556	$213.56	$213.55	$213.60
Purchase #7	$88.43	13.665%	$100.514	$100.51	$100.50	$100.50
7 purchase totals =	$1,016.20		$1,105.3850	$1,105.39	$1,105.40	$1,105.50