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	$181.87	3.560%	$188.3446	$188.34	$188.35	$188.30
Purchase #2	$142.75	7.811%	$153.9002	$153.90	$153.90	$153.90
Purchase #3	$55.73	11.627%	$62.2097	$62.21	$62.20	$62.20
Purchase #4	$250.40	9.655%	$274.5761	$274.58	$274.60	$274.60
Purchase #5	$70.42	10.797%	$78.0232	$78.02	$78.00	$78.00
Purchase #6	$89.63	7.874%	$96.6875	$96.69	$96.70	$96.70
Purchase #7	$141.26	10.396%	$155.9454	$155.95	$155.95	$155.90
7 purchase totals =	$932.06		$1,009.6867	$1,009.69	$1,009.70	$1,009.60