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	$136.52	8.230%	$147.7556	$147.76	$147.75	$147.80
Purchase #2	$131.89	10.307%	$145.4839	$145.48	$145.50	$145.50
Purchase #3	$55.89	12.713%	$62.9953	$63.00	$63.00	$63.00
Purchase #4	$84.84	13.649%	$96.4198	$96.42	$96.40	$96.40
Purchase #5	$116.76	12.645%	$131.5243	$131.52	$131.50	$131.50
Purchase #6	$82.96	12.558%	$93.3781	$93.38	$93.40	$93.40
Purchase #7	$40.63	7.173%	$43.5444	$43.54	$43.55	$43.50
7 purchase totals =	$649.49		$721.1014	$721.10	$721.10	$721.10