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	$241.59	11.514%	$269.4067	$269.41	$269.40	$269.40
Purchase #2	$161.58	6.275%	$171.7191	$171.72	$171.70	$171.70
Purchase #3	$158.37	4.141%	$164.9281	$164.93	$164.95	$164.90
Purchase #4	$183.83	9.853%	$201.9428	$201.94	$201.95	$201.90
Purchase #5	$6.95	4.806%	$7.284	$7.28	$7.30	$7.30
Purchase #6	$23.48	4.507%	$24.5382	$24.54	$24.55	$24.50
Purchase #7	$250.85	8.297%	$271.663	$271.66	$271.65	$271.70
7 purchase totals =	$1,026.65		$1,111.4819	$1,111.48	$1,111.50	$1,111.40