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	$148.43	4.693%	$155.3958	$155.40	$155.40	$155.40
Purchase #2	$163.50	5.667%	$172.7655	$172.77	$172.75	$172.80
Purchase #3	$30.27	11.211%	$33.6636	$33.66	$33.65	$33.70
Purchase #4	$59.93	12.201%	$67.2421	$67.24	$67.25	$67.20
Purchase #5	$151.35	10.762%	$167.6383	$167.64	$167.65	$167.60
Purchase #6	$104.67	13.663%	$118.9711	$118.97	$118.95	$119.00
Purchase #7	$208.66	5.383%	$219.8922	$219.89	$219.90	$219.90
7 purchase totals =	$866.81		$935.5686	$935.57	$935.55	$935.60