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	$58.33	8.205%	$63.116	$63.12	$63.10	$63.10
Purchase #2	$129.35	11.413%	$144.1127	$144.11	$144.10	$144.10
Purchase #3	$141.42	7.678%	$152.2782	$152.28	$152.30	$152.30
Purchase #4	$162.57	3.659%	$168.5184	$168.52	$168.50	$168.50
Purchase #5	$94.89	4.174%	$98.8507	$98.85	$98.85	$98.90
Purchase #6	$77.43	7.635%	$83.3418	$83.34	$83.35	$83.30
Purchase #7	$58.65	11.290%	$65.2716	$65.27	$65.25	$65.30
7 purchase totals =	$722.64		$775.4894	$775.49	$775.45	$775.50