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	$40.27	8.756%	$43.796	$43.80	$43.80	$43.80
Purchase #2	$45.94	8.554%	$49.8697	$49.87	$49.85	$49.90
Purchase #3	$124.93	9.371%	$136.6372	$136.64	$136.65	$136.60
Purchase #4	$89.52	5.709%	$94.6307	$94.63	$94.65	$94.60
Purchase #5	$88.38	3.433%	$91.4141	$91.41	$91.40	$91.40
Purchase #6	$10.62	10.350%	$11.7192	$11.72	$11.70	$11.70
Purchase #7	$57.73	3.765%	$59.9035	$59.90	$59.90	$59.90
7 purchase totals =	$457.39		$487.9704	$487.97	$487.95	$487.90