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	$97.26	8.555%	$105.5806	$105.58	$105.60	$105.60
Purchase #2	$31.48	7.653%	$33.8892	$33.89	$33.90	$33.90
Purchase #3	$79.56	8.548%	$86.3608	$86.36	$86.35	$86.40
Purchase #4	$203.38	7.328%	$218.2837	$218.28	$218.30	$218.30
Purchase #5	$145.56	6.412%	$154.8933	$154.89	$154.90	$154.90
Purchase #6	$223.77	8.158%	$242.0252	$242.03	$242.05	$242.00
Purchase #7	$32.56	9.472%	$35.6441	$35.64	$35.65	$35.60
7 purchase totals =	$813.57		$876.6769	$876.67	$876.75	$876.70