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	$162.60	13.412%	$184.4079	$184.41	$184.40	$184.40
Purchase #2	$89.37	12.553%	$100.5886	$100.59	$100.60	$100.60
Purchase #3	$150.32	12.772%	$169.5189	$169.52	$169.50	$169.50
Purchase #4	$155.41	8.620%	$168.8063	$168.81	$168.80	$168.80
Purchase #5	$184.38	9.860%	$202.5599	$202.56	$202.55	$202.60
Purchase #6	$15.66	12.261%	$17.5801	$17.58	$17.60	$17.60
Purchase #7	$99.63	11.750%	$111.3365	$111.34	$111.35	$111.30
7 purchase totals =	$857.37		$954.7982	$954.81	$954.80	$954.80