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	$125.37	5.745%	$132.5725	$132.57	$132.55	$132.60
Purchase #2	$51.54	5.570%	$54.4108	$54.41	$54.40	$54.40
Purchase #3	$164.67	8.731%	$179.0473	$179.05	$179.05	$179.00
Purchase #4	$118.88	6.862%	$127.0375	$127.04	$127.05	$127.00
Purchase #5	$82.70	4.584%	$86.491	$86.49	$86.50	$86.50
Purchase #6	$82.85	8.405%	$89.8135	$89.81	$89.80	$89.80
Purchase #7	$138.49	13.260%	$156.8538	$156.85	$156.85	$156.90
7 purchase totals =	$764.50		$826.2264	$826.22	$826.20	$826.20