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	$248.40	13.208%	$281.2087	$281.21	$281.20	$281.20
Purchase #2	$103.46	5.667%	$109.3231	$109.32	$109.30	$109.30
Purchase #3	$77.28	12.385%	$86.8511	$86.85	$86.85	$86.90
Purchase #4	$119.56	7.450%	$128.4672	$128.47	$128.45	$128.50
Purchase #5	$163.46	5.596%	$172.6072	$172.61	$172.60	$172.60
Purchase #6	$59.65	4.469%	$62.3158	$62.32	$62.30	$62.30
Purchase #7	$24.92	6.867%	$26.6313	$26.63	$26.65	$26.60
7 purchase totals =	$796.73		$867.4044	$867.41	$867.35	$867.40