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	$123.45	7.339%	$132.51	$132.51	$132.50	$132.50
Purchase #2	$37.67	5.671%	$39.8063	$39.81	$39.80	$39.80
Purchase #3	$151.39	10.832%	$167.7886	$167.79	$167.80	$167.80
Purchase #4	$141.36	6.378%	$150.3759	$150.38	$150.40	$150.40
Purchase #5	$81.63	12.229%	$91.6125	$91.61	$91.60	$91.60
Purchase #6	$155.54	10.110%	$171.2651	$171.27	$171.25	$171.30
Purchase #7	$234.70	10.827%	$260.111	$260.11	$260.10	$260.10
7 purchase totals =	$925.74		$1,013.4694	$1,013.48	$1,013.45	$1,013.50