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	$237.91	12.559%	$267.7891	$267.79	$267.80	$267.80
Purchase #2	$12.72	12.763%	$14.3435	$14.34	$14.35	$14.30
Purchase #3	$69.31	13.220%	$78.4728	$78.47	$78.45	$78.50
Purchase #4	$166.36	11.863%	$186.0953	$186.10	$186.10	$186.10
Purchase #5	$85.40	5.783%	$90.3387	$90.34	$90.35	$90.30
Purchase #6	$79.62	12.394%	$89.4881	$89.49	$89.50	$89.50
Purchase #7	$136.42	12.121%	$152.9555	$152.96	$152.95	$153.00
7 purchase totals =	$787.74		$879.4830	$879.49	$879.50	$879.50