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	$9.57	6.546%	$10.1965	$10.20	$10.20	$10.20
Purchase #2	$250.42	13.846%	$285.0932	$285.09	$285.10	$285.10
Purchase #3	$162.32	12.415%	$182.472	$182.47	$182.45	$182.50
Purchase #4	$85.80	6.455%	$91.3384	$91.34	$91.35	$91.30
Purchase #5	$64.72	4.439%	$67.5929	$67.59	$67.60	$67.60
Purchase #6	$148.79	4.864%	$156.0271	$156.03	$156.05	$156.00
Purchase #7	$130.95	6.382%	$139.3072	$139.31	$139.30	$139.30
7 purchase totals =	$852.57		$932.0273	$932.03	$932.05	$932.00