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	$75.33	13.155%	$85.2397	$85.24	$85.25	$85.20
Purchase #2	$178.62	12.286%	$200.5653	$200.57	$200.55	$200.60
Purchase #3	$143.61	4.539%	$150.1285	$150.13	$150.15	$150.10
Purchase #4	$22.76	10.173%	$25.0754	$25.08	$25.10	$25.10
Purchase #5	$111.39	8.600%	$120.9695	$120.97	$120.95	$121.00
Purchase #6	$156.32	13.189%	$176.937	$176.94	$176.95	$176.90
Purchase #7	$249.29	13.273%	$282.3783	$282.38	$282.40	$282.40
7 purchase totals =	$937.32		$1,041.2937	$1,041.31	$1,041.35	$1,041.30