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	$98.69	13.348%	$111.8631	$111.86	$111.85	$111.90
Purchase #2	$140.31	4.181%	$146.1764	$146.18	$146.20	$146.20
Purchase #3	$63.50	9.272%	$69.3877	$69.39	$69.40	$69.40
Purchase #4	$145.84	7.659%	$157.0099	$157.01	$157.00	$157.00
Purchase #5	$145.29	6.322%	$154.4752	$154.48	$154.50	$154.50
Purchase #6	$88.47	3.171%	$91.2754	$91.28	$91.30	$91.30
Purchase #7	$144.28	6.396%	$153.5081	$153.51	$153.50	$153.50
7 purchase totals =	$826.38		$883.6958	$883.71	$883.75	$883.80