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	$225.57	8.446%	$244.6216	$244.62	$244.60	$244.60
Purchase #2	$73.40	12.568%	$82.6249	$82.62	$82.60	$82.60
Purchase #3	$133.96	6.607%	$142.8107	$142.81	$142.80	$142.80
Purchase #4	$153.97	10.245%	$169.7442	$169.74	$169.75	$169.70
Purchase #5	$142.59	10.145%	$157.0558	$157.06	$157.05	$157.10
Purchase #6	$123.82	12.657%	$139.4919	$139.49	$139.50	$139.50
Purchase #7	$105.60	7.500%	$113.52	$113.52	$113.50	$113.50
7 purchase totals =	$958.91		$1,049.8691	$1,049.86	$1,049.80	$1,049.80