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	$165.57	4.423%	$172.8932	$172.89	$172.90	$172.90
Purchase #2	$13.69	5.676%	$14.467	$14.47	$14.45	$14.50
Purchase #3	$242.99	6.616%	$259.0662	$259.07	$259.05	$259.10
Purchase #4	$121.74	11.713%	$135.9994	$136.00	$136.00	$136.00
Purchase #5	$220.73	5.710%	$233.3337	$233.33	$233.35	$233.30
Purchase #6	$76.85	12.497%	$86.4539	$86.45	$86.45	$86.50
Purchase #7	$100.50	3.207%	$103.723	$103.72	$103.70	$103.70
7 purchase totals =	$942.07		$1,005.9364	$1,005.93	$1,005.90	$1,006.00