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	$204.74	4.283%	$213.509	$213.51	$213.50	$213.50
Purchase #2	$142.72	13.665%	$162.2227	$162.22	$162.20	$162.20
Purchase #3	$85.25	9.434%	$93.2925	$93.29	$93.30	$93.30
Purchase #4	$194.38	11.545%	$216.8212	$216.82	$216.80	$216.80
Purchase #5	$119.55	6.426%	$127.2323	$127.23	$127.25	$127.20
Purchase #6	$29.81	13.681%	$33.8883	$33.89	$33.90	$33.90
Purchase #7	$52.29	11.386%	$58.2437	$58.24	$58.25	$58.20
7 purchase totals =	$828.74		$905.2097	$905.20	$905.20	$905.10