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	$78.37	9.597%	$85.8912	$85.89	$85.90	$85.90
Purchase #2	$173.88	3.220%	$179.4789	$179.48	$179.50	$179.50
Purchase #3	$21.61	8.709%	$23.492	$23.49	$23.50	$23.50
Purchase #4	$26.43	7.653%	$28.4527	$28.45	$28.45	$28.50
Purchase #5	$141.66	12.275%	$159.0488	$159.05	$159.05	$159.00
Purchase #6	$173.92	4.174%	$181.1794	$181.18	$181.20	$181.20
Purchase #7	$98.55	3.357%	$101.8583	$101.86	$101.85	$101.90
7 purchase totals =	$714.42		$759.4013	$759.40	$759.45	$759.50