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	$233.66	9.744%	$256.4278	$256.43	$256.45	$256.40
Purchase #2	$67.44	9.380%	$73.7659	$73.77	$73.75	$73.80
Purchase #3	$43.50	7.257%	$46.6568	$46.66	$46.65	$46.70
Purchase #4	$44.79	11.412%	$49.9014	$49.90	$49.90	$49.90
Purchase #5	$175.96	5.492%	$185.6237	$185.62	$185.60	$185.60
Purchase #6	$10.73	11.174%	$11.929	$11.93	$11.95	$11.90
Purchase #7	$42.30	7.398%	$45.4294	$45.43	$45.45	$45.40
7 purchase totals =	$618.38		$669.7340	$669.74	$669.75	$669.70