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	$60.45	7.866%	$65.205	$65.21	$65.20	$65.20
Purchase #2	$78.72	4.167%	$82.0003	$82.00	$82.00	$82.00
Purchase #3	$195.33	10.540%	$215.9178	$215.92	$215.90	$215.90
Purchase #4	$82.42	11.384%	$91.8027	$91.80	$91.80	$91.80
Purchase #5	$250.45	12.230%	$281.08	$281.08	$281.10	$281.10
Purchase #6	$53.66	9.119%	$58.5533	$58.55	$58.55	$58.60
Purchase #7	$33.74	10.218%	$37.1876	$37.19	$37.20	$37.20
7 purchase totals =	$754.77		$831.7467	$831.75	$831.75	$831.80