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	$141.74	6.271%	$150.6285	$150.63	$150.65	$150.60
Purchase #2	$62.55	13.577%	$71.0424	$71.04	$71.05	$71.00
Purchase #3	$60.78	8.660%	$66.0435	$66.04	$66.05	$66.00
Purchase #4	$50.27	5.220%	$52.8941	$52.89	$52.90	$52.90
Purchase #5	$147.63	5.870%	$156.2959	$156.30	$156.30	$156.30
Purchase #6	$66.66	11.135%	$74.0826	$74.08	$74.10	$74.10
Purchase #7	$132.57	6.698%	$141.4495	$141.45	$141.45	$141.40
7 purchase totals =	$662.20		$712.4365	$712.43	$712.50	$712.30