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	$189.48	8.492%	$205.5706	$205.57	$205.55	$205.60
Purchase #2	$56.58	13.793%	$64.3841	$64.38	$64.40	$64.40
Purchase #3	$40.77	5.574%	$43.0425	$43.04	$43.05	$43.00
Purchase #4	$63.82	12.678%	$71.9111	$71.91	$71.90	$71.90
Purchase #5	$87.51	3.145%	$90.2622	$90.26	$90.25	$90.30
Purchase #6	$213.85	9.194%	$233.5114	$233.51	$233.50	$233.50
Purchase #7	$235.64	12.456%	$264.9913	$264.99	$265.00	$265.00
7 purchase totals =	$887.65		$973.6732	$973.66	$973.65	$973.70