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	$120.34	13.717%	$136.847	$136.85	$136.85	$136.80
Purchase #2	$49.44	5.338%	$52.0791	$52.08	$52.10	$52.10
Purchase #3	$73.89	11.514%	$82.3977	$82.40	$82.40	$82.40
Purchase #4	$221.87	3.604%	$229.8662	$229.87	$229.85	$229.90
Purchase #5	$52.53	12.553%	$59.1241	$59.12	$59.10	$59.10
Purchase #6	$88.28	11.631%	$98.5478	$98.55	$98.55	$98.50
Purchase #7	$124.40	11.222%	$138.3602	$138.36	$138.35	$138.40
7 purchase totals =	$730.75		$797.2221	$797.23	$797.20	$797.20