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	$214.86	4.169%	$223.8175	$223.82	$223.80	$223.80
Purchase #2	$169.70	13.666%	$192.8912	$192.89	$192.90	$192.90
Purchase #3	$166.27	12.393%	$186.8758	$186.88	$186.90	$186.90
Purchase #4	$132.33	8.512%	$143.5939	$143.59	$143.60	$143.60
Purchase #5	$13.37	11.417%	$14.8965	$14.90	$14.90	$14.90
Purchase #6	$74.35	10.868%	$82.4304	$82.43	$82.45	$82.40
Purchase #7	$248.56	8.459%	$269.5857	$269.59	$269.60	$269.60
7 purchase totals =	$1,019.44		$1,114.0910	$1,114.10	$1,114.15	$1,114.10