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	$143.62	9.814%	$157.7149	$157.71	$157.70	$157.70
Purchase #2	$136.48	4.204%	$142.2176	$142.22	$142.20	$142.20
Purchase #3	$25.71	5.610%	$27.1523	$27.15	$27.15	$27.20
Purchase #4	$6.62	11.243%	$7.3643	$7.36	$7.35	$7.40
Purchase #5	$91.31	9.441%	$99.9306	$99.93	$99.95	$99.90
Purchase #6	$53.59	5.629%	$56.6066	$56.61	$56.60	$56.60
Purchase #7	$126.89	11.524%	$141.5128	$141.51	$141.50	$141.50
7 purchase totals =	$584.22		$632.4991	$632.49	$632.45	$632.50