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	$144.66	12.610%	$162.9016	$162.90	$162.90	$162.90
Purchase #2	$231.78	12.218%	$260.0989	$260.10	$260.10	$260.10
Purchase #3	$94.78	4.379%	$98.9304	$98.93	$98.95	$98.90
Purchase #4	$27.69	8.105%	$29.9343	$29.93	$29.95	$29.90
Purchase #5	$193.30	10.379%	$213.3626	$213.36	$213.35	$213.40
Purchase #6	$239.52	12.667%	$269.86	$269.86	$269.85	$269.90
Purchase #7	$67.96	13.134%	$76.8859	$76.89	$76.90	$76.90
7 purchase totals =	$999.69		$1,111.9737	$1,111.97	$1,112.00	$1,112.00