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	$117.66	12.568%	$132.4475	$132.45	$132.45	$132.40
Purchase #2	$159.47	10.762%	$176.6322	$176.63	$176.65	$176.60
Purchase #3	$69.84	12.707%	$78.7146	$78.71	$78.70	$78.70
Purchase #4	$70.84	10.607%	$78.354	$78.35	$78.35	$78.40
Purchase #5	$245.98	9.708%	$269.8597	$269.86	$269.85	$269.90
Purchase #6	$109.36	9.599%	$119.8575	$119.86	$119.85	$119.90
Purchase #7	$197.45	10.116%	$217.424	$217.42	$217.40	$217.40
7 purchase totals =	$970.60		$1,073.2895	$1,073.28	$1,073.25	$1,073.30