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	$178.37	7.345%	$191.4713	$191.47	$191.45	$191.50
Purchase #2	$240.66	11.129%	$267.4431	$267.44	$267.45	$267.40
Purchase #3	$184.39	12.781%	$207.9569	$207.96	$207.95	$208.00
Purchase #4	$76.98	6.279%	$81.8136	$81.81	$81.80	$81.80
Purchase #5	$168.73	4.380%	$176.1204	$176.12	$176.10	$176.10
Purchase #6	$150.70	3.156%	$155.4561	$155.46	$155.45	$155.50
Purchase #7	$29.32	7.732%	$31.587	$31.59	$31.60	$31.60
7 purchase totals =	$1,029.15		$1,111.8484	$1,111.85	$1,111.80	$1,111.90