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	$142.80	13.576%	$162.1865	$162.19	$162.20	$162.20
Purchase #2	$54.42	4.594%	$56.9201	$56.92	$56.90	$56.90
Purchase #3	$36.48	12.234%	$40.943	$40.94	$40.95	$40.90
Purchase #4	$155.67	13.420%	$176.5609	$176.56	$176.55	$176.60
Purchase #5	$168.87	9.109%	$184.2524	$184.25	$184.25	$184.30
Purchase #6	$145.86	9.607%	$159.8728	$159.87	$159.85	$159.90
Purchase #7	$237.82	10.294%	$262.3012	$262.30	$262.30	$262.30
7 purchase totals =	$941.92		$1,043.0369	$1,043.03	$1,043.00	$1,043.10