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	$73.51	13.618%	$83.5206	$83.52	$83.50	$83.50
Purchase #2	$52.38	4.746%	$54.866	$54.87	$54.85	$54.90
Purchase #3	$92.90	12.873%	$104.859	$104.86	$104.85	$104.90
Purchase #4	$60.94	9.235%	$66.5678	$66.57	$66.55	$66.60
Purchase #5	$220.78	3.557%	$228.6331	$228.63	$228.65	$228.60
Purchase #6	$225.50	11.283%	$250.9432	$250.94	$250.95	$250.90
Purchase #7	$85.37	12.808%	$96.3042	$96.30	$96.30	$96.30
7 purchase totals =	$811.38		$885.6939	$885.69	$885.65	$885.70