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	$144.86	10.152%	$159.5662	$159.57	$159.55	$159.60
Purchase #2	$102.38	13.805%	$116.5136	$116.51	$116.50	$116.50
Purchase #3	$38.93	10.412%	$42.9834	$42.98	$43.00	$43.00
Purchase #4	$239.61	12.759%	$270.1818	$270.18	$270.20	$270.20
Purchase #5	$144.58	5.357%	$152.3252	$152.33	$152.35	$152.30
Purchase #6	$242.35	6.275%	$257.5575	$257.56	$257.55	$257.60
Purchase #7	$72.35	6.677%	$77.1808	$77.18	$77.20	$77.20
7 purchase totals =	$985.06		$1,076.3085	$1,076.31	$1,076.35	$1,076.40