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	$38.77	5.437%	$40.8779	$40.88	$40.90	$40.90
Purchase #2	$68.41	6.300%	$72.7198	$72.72	$72.70	$72.70
Purchase #3	$184.55	4.794%	$193.3973	$193.40	$193.40	$193.40
Purchase #4	$40.43	13.502%	$45.8889	$45.89	$45.90	$45.90
Purchase #5	$212.26	9.858%	$233.1846	$233.18	$233.20	$233.20
Purchase #6	$51.54	8.868%	$56.1106	$56.11	$56.10	$56.10
Purchase #7	$12.79	9.218%	$13.969	$13.97	$13.95	$14.00
7 purchase totals =	$608.75		$656.1481	$656.15	$656.15	$656.20