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	$85.48	9.383%	$93.5006	$93.50	$93.50	$93.50
Purchase #2	$139.63	10.421%	$154.1808	$154.18	$154.20	$154.20
Purchase #3	$199.85	13.739%	$227.3074	$227.31	$227.30	$227.30
Purchase #4	$28.73	3.268%	$29.6689	$29.67	$29.65	$29.70
Purchase #5	$239.39	6.720%	$255.477	$255.48	$255.50	$255.50
Purchase #6	$61.38	10.641%	$67.9114	$67.91	$67.90	$67.90
Purchase #7	$19.83	9.783%	$21.77	$21.77	$21.75	$21.80
7 purchase totals =	$774.29		$849.8161	$849.82	$849.80	$849.90