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	$50.59	8.510%	$54.8952	$54.90	$54.90	$54.90
Purchase #2	$36.78	11.416%	$40.9788	$40.98	$41.00	$41.00
Purchase #3	$99.78	11.350%	$111.105	$111.11	$111.10	$111.10
Purchase #4	$206.53	4.615%	$216.0614	$216.06	$216.05	$216.10
Purchase #5	$183.57	3.561%	$190.1069	$190.11	$190.10	$190.10
Purchase #6	$66.36	8.515%	$72.0106	$72.01	$72.00	$72.00
Purchase #7	$36.70	9.632%	$40.2349	$40.23	$40.25	$40.20
7 purchase totals =	$680.31		$725.3928	$725.40	$725.40	$725.40