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	$38.39	7.786%	$41.379	$41.38	$41.40	$41.40
Purchase #2	$60.25	8.736%	$65.5134	$65.51	$65.50	$65.50
Purchase #3	$168.86	10.713%	$186.95	$186.95	$186.95	$187.00
Purchase #4	$106.81	11.236%	$118.8112	$118.81	$118.80	$118.80
Purchase #5	$250.86	13.726%	$285.293	$285.29	$285.30	$285.30
Purchase #6	$65.54	8.378%	$71.0309	$71.03	$71.05	$71.00
Purchase #7	$235.67	10.152%	$259.5952	$259.60	$259.60	$259.60
7 purchase totals =	$926.38		$1,028.5727	$1,028.57	$1,028.60	$1,028.60