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	$94.97	7.124%	$101.7357	$101.74	$101.75	$101.70
Purchase #2	$17.72	11.482%	$19.7546	$19.75	$19.75	$19.80
Purchase #3	$129.83	5.863%	$137.4419	$137.44	$137.45	$137.40
Purchase #4	$26.59	9.708%	$29.1714	$29.17	$29.15	$29.20
Purchase #5	$57.74	3.726%	$59.8914	$59.89	$59.90	$59.90
Purchase #6	$154.59	13.129%	$174.8861	$174.89	$174.90	$174.90
Purchase #7	$73.90	11.140%	$82.1325	$82.13	$82.15	$82.10
7 purchase totals =	$555.34		$605.0136	$605.01	$605.05	$605.00