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	$160.32	4.347%	$167.2891	$167.29	$167.30	$167.30
Purchase #2	$54.86	8.405%	$59.471	$59.47	$59.45	$59.50
Purchase #3	$230.25	10.757%	$255.018	$255.02	$255.00	$255.00
Purchase #4	$79.90	4.620%	$83.5914	$83.59	$83.60	$83.60
Purchase #5	$112.48	9.853%	$123.5627	$123.56	$123.55	$123.60
Purchase #6	$142.28	12.838%	$160.5459	$160.55	$160.55	$160.50
Purchase #7	$21.96	6.700%	$23.4313	$23.43	$23.45	$23.40
7 purchase totals =	$802.05		$872.9094	$872.91	$872.90	$872.90