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	$52.73	13.678%	$59.9424	$59.94	$59.95	$59.90
Purchase #2	$192.40	13.520%	$218.4125	$218.41	$218.40	$218.40
Purchase #3	$91.95	11.259%	$102.3027	$102.30	$102.30	$102.30
Purchase #4	$139.67	11.307%	$155.4625	$155.46	$155.45	$155.50
Purchase #5	$104.99	6.163%	$111.4605	$111.46	$111.45	$111.50
Purchase #6	$80.40	12.118%	$90.1429	$90.14	$90.15	$90.10
Purchase #7	$209.97	7.481%	$225.6779	$225.68	$225.70	$225.70
7 purchase totals =	$872.11		$963.4014	$963.39	$963.40	$963.40