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	$12.89	10.632%	$14.2605	$14.26	$14.25	$14.30
Purchase #2	$157.64	13.618%	$179.1074	$179.11	$179.10	$179.10
Purchase #3	$84.61	12.487%	$95.1753	$95.18	$95.20	$95.20
Purchase #4	$62.71	7.117%	$67.1731	$67.17	$67.15	$67.20
Purchase #5	$71.85	9.516%	$78.6872	$78.69	$78.70	$78.70
Purchase #6	$125.35	11.783%	$140.12	$140.12	$140.10	$140.10
Purchase #7	$27.84	13.307%	$31.5447	$31.54	$31.55	$31.50
7 purchase totals =	$542.89		$606.0682	$606.07	$606.05	$606.10