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	$72.55	13.444%	$82.3036	$82.30	$82.30	$82.30
Purchase #2	$114.25	7.735%	$123.0872	$123.09	$123.10	$123.10
Purchase #3	$52.29	11.115%	$58.102	$58.10	$58.10	$58.10
Purchase #4	$161.30	13.431%	$182.9642	$182.96	$182.95	$183.00
Purchase #5	$77.62	6.473%	$82.6443	$82.64	$82.65	$82.60
Purchase #6	$163.96	13.274%	$185.7241	$185.72	$185.70	$185.70
Purchase #7	$216.30	7.166%	$231.8001	$231.80	$231.80	$231.80
7 purchase totals =	$858.27		$946.6255	$946.61	$946.60	$946.60