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	$241.48	9.741%	$265.0026	$265.00	$265.00	$265.00
Purchase #2	$188.84	3.253%	$194.983	$194.98	$195.00	$195.00
Purchase #3	$229.57	4.766%	$240.5113	$240.51	$240.50	$240.50
Purchase #4	$36.65	11.715%	$40.9435	$40.94	$40.95	$40.90
Purchase #5	$162.84	3.723%	$168.9025	$168.90	$168.90	$168.90
Purchase #6	$33.55	8.715%	$36.4739	$36.47	$36.45	$36.50
Purchase #7	$116.45	6.351%	$123.8457	$123.85	$123.85	$123.80
7 purchase totals =	$1,009.38		$1,070.6625	$1,070.65	$1,070.65	$1,070.60