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	$47.66	10.345%	$52.5904	$52.59	$52.60	$52.60
Purchase #2	$137.86	4.296%	$143.7825	$143.78	$143.80	$143.80
Purchase #3	$63.48	12.501%	$71.4156	$71.42	$71.40	$71.40
Purchase #4	$107.68	4.439%	$112.4599	$112.46	$112.45	$112.50
Purchase #5	$227.84	9.679%	$249.8926	$249.89	$249.90	$249.90
Purchase #6	$33.27	10.796%	$36.8618	$36.86	$36.85	$36.90
Purchase #7	$152.62	4.616%	$159.6649	$159.66	$159.65	$159.70
7 purchase totals =	$770.41		$826.6677	$826.66	$826.65	$826.80