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	$62.59	5.372%	$65.9523	$65.95	$65.95	$66.00
Purchase #2	$40.28	4.392%	$42.0491	$42.05	$42.05	$42.00
Purchase #3	$129.85	5.483%	$136.9697	$136.97	$136.95	$137.00
Purchase #4	$228.26	4.489%	$238.5066	$238.51	$238.50	$238.50
Purchase #5	$205.85	9.584%	$225.5787	$225.58	$225.60	$225.60
Purchase #6	$104.77	7.576%	$112.7074	$112.71	$112.70	$112.70
Purchase #7	$102.78	6.342%	$109.2983	$109.30	$109.30	$109.30
7 purchase totals =	$874.38		$931.0621	$931.07	$931.05	$931.10