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	$172.69	9.410%	$188.9401	$188.94	$188.95	$188.90
Purchase #2	$32.55	9.831%	$35.75	$35.75	$35.75	$35.80
Purchase #3	$141.34	13.563%	$160.5099	$160.51	$160.50	$160.50
Purchase #4	$131.41	10.330%	$144.9847	$144.98	$145.00	$145.00
Purchase #5	$138.86	12.363%	$156.0273	$156.03	$156.05	$156.00
Purchase #6	$202.32	9.151%	$220.8343	$220.83	$220.85	$220.80
Purchase #7	$17.57	5.348%	$18.5096	$18.51	$18.50	$18.50
7 purchase totals =	$836.74		$925.5559	$925.55	$925.60	$925.50