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	$244.61	3.629%	$253.4869	$253.49	$253.50	$253.50
Purchase #2	$141.50	13.844%	$161.0893	$161.09	$161.10	$161.10
Purchase #3	$80.39	13.639%	$91.3544	$91.35	$91.35	$91.40
Purchase #4	$11.48	7.182%	$12.3045	$12.30	$12.30	$12.30
Purchase #5	$125.82	13.329%	$142.5905	$142.59	$142.60	$142.60
Purchase #6	$156.71	3.695%	$162.5004	$162.50	$162.50	$162.50
Purchase #7	$144.29	6.626%	$153.8507	$153.85	$153.85	$153.90
7 purchase totals =	$904.80		$977.1767	$977.17	$977.20	$977.30