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	$23.61	5.394%	$24.8835	$24.88	$24.90	$24.90
Purchase #2	$179.81	5.577%	$189.838	$189.84	$189.85	$189.80
Purchase #3	$58.52	12.408%	$65.7812	$65.78	$65.80	$65.80
Purchase #4	$208.50	3.729%	$216.275	$216.28	$216.30	$216.30
Purchase #5	$203.33	3.245%	$209.9281	$209.93	$209.95	$209.90
Purchase #6	$147.91	7.426%	$158.8938	$158.89	$158.90	$158.90
Purchase #7	$191.39	3.677%	$198.4274	$198.43	$198.45	$198.40
7 purchase totals =	$1,013.07		$1,064.0270	$1,064.03	$1,064.15	$1,064.00