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	$136.40	11.484%	$152.0642	$152.06	$152.05	$152.10
Purchase #2	$236.76	6.203%	$251.4462	$251.45	$251.45	$251.40
Purchase #3	$148.65	12.479%	$167.2	$167.20	$167.20	$167.20
Purchase #4	$127.93	11.626%	$142.8031	$142.80	$142.80	$142.80
Purchase #5	$73.39	6.772%	$78.36	$78.36	$78.35	$78.40
Purchase #6	$54.86	6.439%	$58.3924	$58.39	$58.40	$58.40
Purchase #7	$80.29	9.618%	$88.0123	$88.01	$88.00	$88.00
7 purchase totals =	$858.28		$938.2782	$938.27	$938.25	$938.30