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	$116.27	3.706%	$120.579	$120.58	$120.60	$120.60
Purchase #2	$47.36	6.528%	$50.4517	$50.45	$50.45	$50.50
Purchase #3	$239.50	9.594%	$262.4776	$262.48	$262.50	$262.50
Purchase #4	$219.89	12.484%	$247.3411	$247.34	$247.35	$247.30
Purchase #5	$205.56	7.816%	$221.6266	$221.63	$221.65	$221.60
Purchase #6	$147.78	5.757%	$156.2877	$156.29	$156.30	$156.30
Purchase #7	$33.82	4.475%	$35.3334	$35.33	$35.35	$35.30
7 purchase totals =	$1,010.18		$1,094.0971	$1,094.10	$1,094.20	$1,094.10