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	$31.41	3.379%	$32.4713	$32.47	$32.45	$32.50
Purchase #2	$7.77	13.255%	$8.7999	$8.80	$8.80	$8.80
Purchase #3	$74.59	9.637%	$81.7782	$81.78	$81.80	$81.80
Purchase #4	$173.78	3.645%	$180.1143	$180.11	$180.10	$180.10
Purchase #5	$50.66	9.812%	$55.6308	$55.63	$55.65	$55.60
Purchase #6	$49.25	6.131%	$52.2695	$52.27	$52.25	$52.30
Purchase #7	$82.86	5.493%	$87.4115	$87.41	$87.40	$87.40
7 purchase totals =	$470.32		$498.4755	$498.47	$498.45	$498.50