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	$20.83	8.424%	$22.5847	$22.58	$22.60	$22.60
Purchase #2	$120.69	4.799%	$126.4819	$126.48	$126.50	$126.50
Purchase #3	$99.61	10.284%	$109.8539	$109.85	$109.85	$109.90
Purchase #4	$151.48	3.554%	$156.8636	$156.86	$156.85	$156.90
Purchase #5	$170.71	5.186%	$179.563	$179.56	$179.55	$179.60
Purchase #6	$99.46	13.849%	$113.2342	$113.23	$113.25	$113.20
Purchase #7	$39.36	11.257%	$43.7908	$43.79	$43.80	$43.80
7 purchase totals =	$702.14		$752.3721	$752.35	$752.40	$752.50