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	$128.82	8.661%	$139.9771	$139.98	$140.00	$140.00
Purchase #2	$72.52	8.209%	$78.4732	$78.47	$78.45	$78.50
Purchase #3	$227.74	7.328%	$244.4288	$244.43	$244.45	$244.40
Purchase #4	$164.36	10.397%	$181.4485	$181.45	$181.45	$181.40
Purchase #5	$42.29	3.449%	$43.7486	$43.75	$43.75	$43.70
Purchase #6	$13.26	11.483%	$14.7826	$14.78	$14.80	$14.80
Purchase #7	$207.55	7.239%	$222.5745	$222.57	$222.55	$222.60
7 purchase totals =	$856.54		$925.4333	$925.43	$925.45	$925.40