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	$94.80	8.437%	$102.7983	$102.80	$102.80	$102.80
Purchase #2	$244.82	12.281%	$274.8863	$274.89	$274.90	$274.90
Purchase #3	$189.56	5.711%	$200.3858	$200.39	$200.40	$200.40
Purchase #4	$141.57	10.517%	$156.4589	$156.46	$156.45	$156.50
Purchase #5	$206.59	12.257%	$231.9117	$231.91	$231.90	$231.90
Purchase #6	$44.47	8.495%	$48.2477	$48.25	$48.25	$48.20
Purchase #7	$86.36	5.298%	$90.9354	$90.94	$90.95	$90.90
7 purchase totals =	$1,008.17		$1,105.6241	$1,105.64	$1,105.65	$1,105.60