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	$227.87	7.309%	$244.525	$244.53	$244.55	$244.50
Purchase #2	$117.32	4.646%	$122.7707	$122.77	$122.75	$122.80
Purchase #3	$106.96	12.499%	$120.3289	$120.33	$120.35	$120.30
Purchase #4	$239.52	5.699%	$253.1702	$253.17	$253.15	$253.20
Purchase #5	$27.81	13.639%	$31.603	$31.60	$31.60	$31.60
Purchase #6	$215.60	5.401%	$227.2446	$227.24	$227.25	$227.20
Purchase #7	$88.95	13.364%	$100.8373	$100.84	$100.85	$100.80
7 purchase totals =	$1,024.03		$1,100.4797	$1,100.48	$1,100.50	$1,100.40