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	$250.89	4.153%	$261.3095	$261.31	$261.30	$261.30
Purchase #2	$24.61	9.270%	$26.8913	$26.89	$26.90	$26.90
Purchase #3	$108.96	7.690%	$117.339	$117.34	$117.35	$117.30
Purchase #4	$150.74	7.370%	$161.8495	$161.85	$161.85	$161.80
Purchase #5	$38.56	10.664%	$42.672	$42.67	$42.65	$42.70
Purchase #6	$9.36	13.208%	$10.5963	$10.60	$10.60	$10.60
Purchase #7	$119.91	3.313%	$123.8826	$123.88	$123.90	$123.90
7 purchase totals =	$703.03		$744.5402	$744.54	$744.55	$744.50