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	$113.41	13.628%	$128.8655	$128.87	$128.85	$128.90
Purchase #2	$244.39	13.759%	$278.0156	$278.02	$278.00	$278.00
Purchase #3	$60.72	7.214%	$65.1003	$65.10	$65.10	$65.10
Purchase #4	$49.75	4.362%	$51.9201	$51.92	$51.90	$51.90
Purchase #5	$125.25	13.874%	$142.6272	$142.63	$142.65	$142.60
Purchase #6	$112.87	9.686%	$123.8026	$123.80	$123.80	$123.80
Purchase #7	$247.91	8.554%	$269.1162	$269.12	$269.10	$269.10
7 purchase totals =	$954.30		$1,059.4475	$1,059.46	$1,059.40	$1,059.40