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	$90.27	7.511%	$97.0502	$97.05	$97.05	$97.10
Purchase #2	$73.74	12.131%	$82.6854	$82.69	$82.70	$82.70
Purchase #3	$105.77	5.484%	$111.5704	$111.57	$111.55	$111.60
Purchase #4	$189.57	10.182%	$208.872	$208.87	$208.85	$208.90
Purchase #5	$72.93	11.104%	$81.0281	$81.03	$81.05	$81.00
Purchase #6	$9.65	7.120%	$10.3371	$10.34	$10.35	$10.30
Purchase #7	$52.35	10.215%	$57.6976	$57.70	$57.70	$57.70
7 purchase totals =	$594.28		$649.2408	$649.25	$649.25	$649.30