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	$119.51	13.476%	$135.6152	$135.62	$135.60	$135.60
Purchase #2	$32.72	11.486%	$36.4782	$36.48	$36.50	$36.50
Purchase #3	$87.52	3.288%	$90.3977	$90.40	$90.40	$90.40
Purchase #4	$75.72	3.864%	$78.6458	$78.65	$78.65	$78.60
Purchase #5	$182.68	4.723%	$191.308	$191.31	$191.30	$191.30
Purchase #6	$157.44	3.462%	$162.8906	$162.89	$162.90	$162.90
Purchase #7	$166.62	6.530%	$177.5003	$177.50	$177.50	$177.50
7 purchase totals =	$822.21		$872.8358	$872.85	$872.85	$872.80