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	$126.65	12.563%	$142.561	$142.56	$142.55	$142.60
Purchase #2	$220.41	8.381%	$238.8826	$238.88	$238.90	$238.90
Purchase #3	$154.65	9.227%	$168.9196	$168.92	$168.90	$168.90
Purchase #4	$137.26	11.785%	$153.4361	$153.44	$153.45	$153.40
Purchase #5	$125.80	12.817%	$141.9238	$141.92	$141.90	$141.90
Purchase #6	$26.56	4.252%	$27.6893	$27.69	$27.70	$27.70
Purchase #7	$105.85	3.669%	$109.7336	$109.73	$109.75	$109.70
7 purchase totals =	$897.18		$983.1460	$983.14	$983.15	$983.10