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	$115.27	7.265%	$123.6444	$123.64	$123.65	$123.60
Purchase #2	$118.45	12.167%	$132.8618	$132.86	$132.85	$132.90
Purchase #3	$37.45	4.387%	$39.0929	$39.09	$39.10	$39.10
Purchase #4	$242.61	6.375%	$258.0764	$258.08	$258.10	$258.10
Purchase #5	$130.53	12.838%	$147.2874	$147.29	$147.30	$147.30
Purchase #6	$244.90	8.321%	$265.2781	$265.28	$265.30	$265.30
Purchase #7	$134.41	13.276%	$152.2543	$152.25	$152.25	$152.30
7 purchase totals =	$1,023.62		$1,118.4953	$1,118.49	$1,118.55	$1,118.60