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	$173.26	13.281%	$196.2707	$196.27	$196.25	$196.30
Purchase #2	$129.81	4.248%	$135.3243	$135.32	$135.30	$135.30
Purchase #3	$144.35	7.836%	$155.6613	$155.66	$155.65	$155.70
Purchase #4	$116.49	8.579%	$126.4837	$126.48	$126.50	$126.50
Purchase #5	$79.48	10.729%	$88.0074	$88.01	$88.00	$88.00
Purchase #6	$81.79	9.140%	$89.2656	$89.27	$89.25	$89.30
Purchase #7	$152.34	12.849%	$171.9142	$171.91	$171.90	$171.90
7 purchase totals =	$877.52		$962.9272	$962.92	$962.85	$963.00