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	$244.58	8.732%	$265.9367	$265.94	$265.95	$265.90
Purchase #2	$79.76	7.735%	$85.9294	$85.93	$85.95	$85.90
Purchase #3	$45.34	8.773%	$49.3177	$49.32	$49.30	$49.30
Purchase #4	$80.49	12.284%	$90.3774	$90.38	$90.40	$90.40
Purchase #5	$62.26	3.645%	$64.5294	$64.53	$64.55	$64.50
Purchase #6	$241.60	11.523%	$269.4396	$269.44	$269.45	$269.40
Purchase #7	$201.38	7.698%	$216.8822	$216.88	$216.90	$216.90
7 purchase totals =	$955.41		$1,042.4124	$1,042.42	$1,042.50	$1,042.30