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	$171.29	8.171%	$185.2861	$185.29	$185.30	$185.30
Purchase #2	$136.93	4.447%	$143.0193	$143.02	$143.00	$143.00
Purchase #3	$163.97	8.680%	$178.2026	$178.20	$178.20	$178.20
Purchase #4	$79.58	4.700%	$83.3203	$83.32	$83.30	$83.30
Purchase #5	$126.73	3.643%	$131.3468	$131.35	$131.35	$131.30
Purchase #6	$71.76	9.509%	$78.5837	$78.58	$78.60	$78.60
Purchase #7	$238.74	4.107%	$248.5451	$248.55	$248.55	$248.50
7 purchase totals =	$989.00		$1,048.3039	$1,048.31	$1,048.30	$1,048.20