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	$55.98	5.517%	$59.0684	$59.07	$59.05	$59.10
Purchase #2	$47.65	3.387%	$49.2639	$49.26	$49.25	$49.30
Purchase #3	$83.68	5.726%	$88.4715	$88.47	$88.45	$88.50
Purchase #4	$72.86	11.800%	$81.4575	$81.46	$81.45	$81.50
Purchase #5	$197.76	13.200%	$223.8643	$223.86	$223.85	$223.90
Purchase #6	$189.54	11.108%	$210.5941	$210.59	$210.60	$210.60
Purchase #7	$197.31	4.751%	$206.6842	$206.68	$206.70	$206.70
7 purchase totals =	$844.78		$919.4039	$919.39	$919.35	$919.60