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	$217.52	7.132%	$233.0335	$233.03	$233.05	$233.00
Purchase #2	$55.26	13.823%	$62.8986	$62.90	$62.90	$62.90
Purchase #3	$54.25	10.274%	$59.8236	$59.82	$59.80	$59.80
Purchase #4	$202.38	11.115%	$224.8745	$224.87	$224.85	$224.90
Purchase #5	$9.89	7.306%	$10.6126	$10.61	$10.60	$10.60
Purchase #6	$179.46	10.691%	$198.6461	$198.65	$198.65	$198.60
Purchase #7	$137.74	5.864%	$145.8171	$145.82	$145.80	$145.80
7 purchase totals =	$856.50		$935.7060	$935.70	$935.65	$935.60