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	$41.63	5.459%	$43.9026	$43.90	$43.90	$43.90
Purchase #2	$198.61	13.395%	$225.2138	$225.21	$225.20	$225.20
Purchase #3	$233.88	10.103%	$257.5089	$257.51	$257.50	$257.50
Purchase #4	$117.58	13.812%	$133.8201	$133.82	$133.80	$133.80
Purchase #5	$34.50	4.653%	$36.1053	$36.11	$36.10	$36.10
Purchase #6	$117.96	11.160%	$131.1243	$131.12	$131.10	$131.10
Purchase #7	$221.30	5.736%	$233.9938	$233.99	$234.00	$234.00
7 purchase totals =	$965.46		$1,061.6688	$1,061.66	$1,061.60	$1,061.60