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	$103.64	5.340%	$109.1744	$109.17	$109.15	$109.20
Purchase #2	$84.25	13.271%	$95.4308	$95.43	$95.45	$95.40
Purchase #3	$249.74	13.147%	$282.5733	$282.57	$282.55	$282.60
Purchase #4	$35.84	3.508%	$37.0973	$37.10	$37.10	$37.10
Purchase #5	$131.73	12.677%	$148.4294	$148.43	$148.45	$148.40
Purchase #6	$179.38	4.681%	$187.7768	$187.78	$187.80	$187.80
Purchase #7	$14.85	13.446%	$16.8467	$16.85	$16.85	$16.80
7 purchase totals =	$799.43		$877.3287	$877.33	$877.35	$877.30