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	$81.49	13.476%	$92.4716	$92.47	$92.45	$92.50
Purchase #2	$170.34	6.372%	$181.1941	$181.19	$181.20	$181.20
Purchase #3	$180.94	8.650%	$196.5913	$196.59	$196.60	$196.60
Purchase #4	$113.46	8.417%	$123.0099	$123.01	$123.00	$123.00
Purchase #5	$185.69	8.336%	$201.1691	$201.17	$201.15	$201.20
Purchase #6	$178.78	6.802%	$190.9406	$190.94	$190.95	$190.90
Purchase #7	$156.76	7.225%	$168.0859	$168.09	$168.10	$168.10
7 purchase totals =	$1,067.46		$1,153.4625	$1,153.46	$1,153.45	$1,153.50