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	$240.38	6.863%	$256.8773	$256.88	$256.90	$256.90
Purchase #2	$172.34	5.223%	$181.3413	$181.34	$181.35	$181.30
Purchase #3	$103.86	5.650%	$109.7281	$109.73	$109.75	$109.70
Purchase #4	$40.67	11.127%	$45.1954	$45.20	$45.20	$45.20
Purchase #5	$188.76	3.563%	$195.4855	$195.49	$195.50	$195.50
Purchase #6	$17.83	5.552%	$18.8199	$18.82	$18.80	$18.80
Purchase #7	$234.76	11.386%	$261.4898	$261.49	$261.50	$261.50
7 purchase totals =	$998.60		$1,068.9373	$1,068.95	$1,069.00	$1,068.90