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	$230.76	4.729%	$241.6726	$241.67	$241.65	$241.70
Purchase #2	$11.96	5.108%	$12.5709	$12.57	$12.55	$12.60
Purchase #3	$35.45	4.469%	$37.0343	$37.03	$37.05	$37.00
Purchase #4	$73.98	11.310%	$82.3471	$82.35	$82.35	$82.30
Purchase #5	$246.86	4.540%	$258.0674	$258.07	$258.05	$258.10
Purchase #6	$52.87	8.505%	$57.3666	$57.37	$57.35	$57.40
Purchase #7	$190.92	4.667%	$199.8302	$199.83	$199.85	$199.80
7 purchase totals =	$842.80		$888.8891	$888.89	$888.85	$888.90