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	$169.71	7.662%	$182.7132	$182.71	$182.70	$182.70
Purchase #2	$109.93	13.350%	$124.6057	$124.61	$124.60	$124.60
Purchase #3	$58.96	9.631%	$64.6384	$64.64	$64.65	$64.60
Purchase #4	$78.80	10.329%	$86.9393	$86.94	$86.95	$86.90
Purchase #5	$66.83	8.197%	$72.3081	$72.31	$72.30	$72.30
Purchase #6	$219.43	10.213%	$241.8404	$241.84	$241.85	$241.80
Purchase #7	$95.90	13.504%	$108.8503	$108.85	$108.85	$108.90
7 purchase totals =	$799.56		$881.8954	$881.90	$881.90	$881.80