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	$209.27	9.655%	$229.475	$229.48	$229.50	$229.50
Purchase #2	$64.77	3.102%	$66.7792	$66.78	$66.80	$66.80
Purchase #3	$62.76	7.576%	$67.5147	$67.51	$67.50	$67.50
Purchase #4	$50.55	3.393%	$52.2652	$52.27	$52.25	$52.30
Purchase #5	$149.84	3.836%	$155.5879	$155.59	$155.60	$155.60
Purchase #6	$84.50	9.571%	$92.5875	$92.59	$92.60	$92.60
Purchase #7	$16.56	11.590%	$18.4793	$18.48	$18.50	$18.50
7 purchase totals =	$638.25		$682.6888	$682.70	$682.75	$682.80