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	$55.42	7.391%	$59.5161	$59.52	$59.50	$59.50
Purchase #2	$39.52	10.669%	$43.7364	$43.74	$43.75	$43.70
Purchase #3	$36.67	8.194%	$39.6747	$39.67	$39.65	$39.70
Purchase #4	$143.73	7.777%	$154.9079	$154.91	$154.90	$154.90
Purchase #5	$43.82	5.556%	$46.2546	$46.25	$46.25	$46.30
Purchase #6	$12.29	4.822%	$12.8826	$12.88	$12.90	$12.90
Purchase #7	$189.96	13.830%	$216.2315	$216.23	$216.25	$216.20
7 purchase totals =	$521.41		$573.2038	$573.20	$573.20	$573.20