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	$163.68	10.714%	$181.2167	$181.22	$181.20	$181.20
Purchase #2	$46.42	5.810%	$49.117	$49.12	$49.10	$49.10
Purchase #3	$153.39	11.485%	$171.0068	$171.01	$171.00	$171.00
Purchase #4	$136.86	10.849%	$151.7079	$151.71	$151.70	$151.70
Purchase #5	$98.67	5.676%	$104.2705	$104.27	$104.25	$104.30
Purchase #6	$142.46	8.264%	$154.2329	$154.23	$154.25	$154.20
Purchase #7	$37.30	12.623%	$42.0084	$42.01	$42.00	$42.00
7 purchase totals =	$778.78		$853.5602	$853.57	$853.50	$853.50