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	$54.70	10.448%	$60.4151	$60.42	$60.40	$60.40
Purchase #2	$147.36	11.573%	$164.414	$164.41	$164.40	$164.40
Purchase #3	$109.55	7.761%	$118.0522	$118.05	$118.05	$118.10
Purchase #4	$141.27	10.671%	$156.3449	$156.34	$156.35	$156.30
Purchase #5	$47.46	9.108%	$51.7827	$51.78	$51.80	$51.80
Purchase #6	$232.93	12.861%	$262.8871	$262.89	$262.90	$262.90
Purchase #7	$240.46	13.732%	$273.48	$273.48	$273.50	$273.50
7 purchase totals =	$973.73		$1,087.3760	$1,087.37	$1,087.40	$1,087.40