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	$140.58	11.111%	$156.1998	$156.20	$156.20	$156.20
Purchase #2	$213.61	7.259%	$229.1159	$229.12	$229.10	$229.10
Purchase #3	$142.27	9.772%	$156.1726	$156.17	$156.15	$156.20
Purchase #4	$121.41	3.602%	$125.7832	$125.78	$125.80	$125.80
Purchase #5	$37.96	10.266%	$41.857	$41.86	$41.85	$41.90
Purchase #6	$12.43	11.782%	$13.8945	$13.89	$13.90	$13.90
Purchase #7	$37.40	12.677%	$42.1412	$42.14	$42.15	$42.10
7 purchase totals =	$705.66		$765.1642	$765.16	$765.15	$765.20