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	$41.72	5.176%	$43.8794	$43.88	$43.90	$43.90
Purchase #2	$196.96	12.555%	$221.6883	$221.69	$221.70	$221.70
Purchase #3	$129.49	11.490%	$144.3684	$144.37	$144.35	$144.40
Purchase #4	$100.48	4.173%	$104.673	$104.67	$104.65	$104.70
Purchase #5	$108.81	10.354%	$120.0762	$120.08	$120.10	$120.10
Purchase #6	$208.30	8.705%	$226.4325	$226.43	$226.45	$226.40
Purchase #7	$233.76	7.128%	$250.4224	$250.42	$250.40	$250.40
7 purchase totals =	$1,019.52		$1,111.5402	$1,111.54	$1,111.55	$1,111.60