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	$60.52	10.872%	$67.0997	$67.10	$67.10	$67.10
Purchase #2	$222.86	3.318%	$230.2545	$230.25	$230.25	$230.30
Purchase #3	$50.36	9.330%	$55.0586	$55.06	$55.05	$55.10
Purchase #4	$145.74	8.731%	$158.4646	$158.46	$158.45	$158.50
Purchase #5	$14.90	11.117%	$16.5564	$16.56	$16.55	$16.60
Purchase #6	$98.67	7.311%	$105.8838	$105.88	$105.90	$105.90
Purchase #7	$79.26	4.168%	$82.5636	$82.56	$82.55	$82.60
7 purchase totals =	$672.31		$715.8812	$715.87	$715.85	$716.10