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	$125.55	6.311%	$133.4735	$133.47	$133.45	$133.50
Purchase #2	$139.82	13.368%	$158.5111	$158.51	$158.50	$158.50
Purchase #3	$36.33	8.564%	$39.4413	$39.44	$39.45	$39.40
Purchase #4	$158.80	5.168%	$167.0068	$167.01	$167.00	$167.00
Purchase #5	$236.42	6.521%	$251.8369	$251.84	$251.85	$251.80
Purchase #6	$159.96	10.486%	$176.7334	$176.73	$176.75	$176.70
Purchase #7	$86.85	3.405%	$89.8072	$89.81	$89.80	$89.80
7 purchase totals =	$943.73		$1,016.8102	$1,016.81	$1,016.80	$1,016.70