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	$85.47	8.172%	$92.4546	$92.45	$92.45	$92.50
Purchase #2	$151.78	7.616%	$163.3396	$163.34	$163.35	$163.30
Purchase #3	$13.61	4.746%	$14.2559	$14.26	$14.25	$14.30
Purchase #4	$112.28	9.741%	$123.2172	$123.22	$123.20	$123.20
Purchase #5	$149.89	8.326%	$162.3698	$162.37	$162.35	$162.40
Purchase #6	$115.77	7.255%	$124.1691	$124.17	$124.15	$124.20
Purchase #7	$77.98	9.639%	$85.4965	$85.50	$85.50	$85.50
7 purchase totals =	$706.78		$765.3027	$765.31	$765.25	$765.40