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	$82.67	5.392%	$87.1276	$87.13	$87.15	$87.10
Purchase #2	$183.75	13.484%	$208.5269	$208.53	$208.55	$208.50
Purchase #3	$40.46	13.194%	$45.7983	$45.80	$45.80	$45.80
Purchase #4	$227.83	12.113%	$255.427	$255.43	$255.45	$255.40
Purchase #5	$185.30	10.192%	$204.1858	$204.19	$204.20	$204.20
Purchase #6	$55.43	5.610%	$58.5396	$58.54	$58.55	$58.50
Purchase #7	$48.87	3.125%	$50.3972	$50.40	$50.40	$50.40
7 purchase totals =	$824.31		$910.0024	$910.02	$910.10	$909.90