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	$196.35	6.179%	$208.4825	$208.48	$208.50	$208.50
Purchase #2	$226.47	7.252%	$242.8936	$242.89	$242.90	$242.90
Purchase #3	$168.79	6.225%	$179.2972	$179.30	$179.30	$179.30
Purchase #4	$90.62	13.806%	$103.131	$103.13	$103.15	$103.10
Purchase #5	$224.38	11.142%	$249.3804	$249.38	$249.40	$249.40
Purchase #6	$34.59	12.597%	$38.9473	$38.95	$38.95	$38.90
Purchase #7	$96.35	8.696%	$104.7286	$104.73	$104.75	$104.70
7 purchase totals =	$1,037.55		$1,126.8606	$1,126.86	$1,126.95	$1,126.80