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	$117.93	6.226%	$125.2723	$125.27	$125.25	$125.30
Purchase #2	$112.73	12.196%	$126.4786	$126.48	$126.50	$126.50
Purchase #3	$240.84	7.683%	$259.3437	$259.34	$259.35	$259.30
Purchase #4	$82.59	9.370%	$90.3287	$90.33	$90.35	$90.30
Purchase #5	$97.69	5.728%	$103.2857	$103.29	$103.30	$103.30
Purchase #6	$130.44	8.476%	$141.4961	$141.50	$141.50	$141.50
Purchase #7	$17.65	4.383%	$18.4236	$18.42	$18.40	$18.40
7 purchase totals =	$799.87		$864.6287	$864.63	$864.65	$864.60