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	$206.54	12.742%	$232.8573	$232.86	$232.85	$232.90
Purchase #2	$128.52	10.792%	$142.3899	$142.39	$142.40	$142.40
Purchase #3	$79.60	12.304%	$89.394	$89.39	$89.40	$89.40
Purchase #4	$113.48	11.601%	$126.6448	$126.64	$126.65	$126.60
Purchase #5	$213.84	11.591%	$238.6262	$238.63	$238.65	$238.60
Purchase #6	$195.58	6.798%	$208.8755	$208.88	$208.90	$208.90
Purchase #7	$58.87	13.408%	$66.7633	$66.76	$66.75	$66.80
7 purchase totals =	$996.43		$1,105.5510	$1,105.55	$1,105.60	$1,105.60