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	$84.54	3.228%	$87.269	$87.27	$87.25	$87.30
Purchase #2	$54.28	11.682%	$60.621	$60.62	$60.60	$60.60
Purchase #3	$206.79	6.297%	$219.8116	$219.81	$219.80	$219.80
Purchase #4	$78.70	10.469%	$86.9391	$86.94	$86.95	$86.90
Purchase #5	$200.96	7.472%	$215.9757	$215.98	$216.00	$216.00
Purchase #6	$98.41	13.388%	$111.5851	$111.59	$111.60	$111.60
Purchase #7	$71.89	8.593%	$78.0675	$78.07	$78.05	$78.10
7 purchase totals =	$795.57		$860.2690	$860.28	$860.25	$860.30