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	$82.92	4.433%	$86.5958	$86.60	$86.60	$86.60
Purchase #2	$105.93	3.309%	$109.4352	$109.44	$109.45	$109.40
Purchase #3	$69.63	13.113%	$78.7606	$78.76	$78.75	$78.80
Purchase #4	$71.74	6.514%	$76.4131	$76.41	$76.40	$76.40
Purchase #5	$40.44	13.394%	$45.8565	$45.86	$45.85	$45.90
Purchase #6	$128.33	3.208%	$132.4468	$132.45	$132.45	$132.40
Purchase #7	$30.74	4.145%	$32.0142	$32.01	$32.00	$32.00
7 purchase totals =	$529.73		$561.5222	$561.53	$561.50	$561.50