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	$24.65	3.323%	$25.4691	$25.47	$25.45	$25.50
Purchase #2	$190.72	3.195%	$196.8135	$196.81	$196.80	$196.80
Purchase #3	$215.32	5.832%	$227.8775	$227.88	$227.90	$227.90
Purchase #4	$210.57	10.295%	$232.2482	$232.25	$232.25	$232.20
Purchase #5	$150.45	11.515%	$167.7743	$167.77	$167.75	$167.80
Purchase #6	$74.44	10.486%	$82.2458	$82.25	$82.25	$82.20
Purchase #7	$85.97	8.317%	$93.1201	$93.12	$93.10	$93.10
7 purchase totals =	$952.12		$1,025.5485	$1,025.55	$1,025.50	$1,025.50