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	$137.57	4.186%	$143.3287	$143.33	$143.35	$143.30
Purchase #2	$18.94	13.419%	$21.4816	$21.48	$21.50	$21.50
Purchase #3	$75.96	9.228%	$82.9696	$82.97	$82.95	$83.00
Purchase #4	$63.60	3.401%	$65.763	$65.76	$65.75	$65.80
Purchase #5	$59.63	11.643%	$66.5727	$66.57	$66.55	$66.60
Purchase #6	$31.88	12.342%	$35.8146	$35.81	$35.80	$35.80
Purchase #7	$56.90	5.446%	$59.9988	$60.00	$60.00	$60.00
7 purchase totals =	$444.48		$475.9290	$475.92	$475.90	$476.00