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	$67.75	13.836%	$77.1239	$77.12	$77.10	$77.10
Purchase #2	$141.69	12.849%	$159.8957	$159.90	$159.90	$159.90
Purchase #3	$88.84	9.776%	$97.525	$97.53	$97.55	$97.50
Purchase #4	$189.46	5.840%	$200.5245	$200.52	$200.50	$200.50
Purchase #5	$52.49	13.393%	$59.52	$59.52	$59.50	$59.50
Purchase #6	$11.50	9.410%	$12.5822	$12.58	$12.60	$12.60
Purchase #7	$67.99	9.790%	$74.6462	$74.65	$74.65	$74.60
7 purchase totals =	$619.72		$681.8175	$681.82	$681.80	$681.70