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	$126.86	9.774%	$139.2593	$139.26	$139.25	$139.30
Purchase #2	$158.83	8.782%	$172.7785	$172.78	$172.80	$172.80
Purchase #3	$156.84	5.148%	$164.9141	$164.91	$164.90	$164.90
Purchase #4	$129.55	12.104%	$145.2307	$145.23	$145.25	$145.20
Purchase #5	$173.53	7.366%	$186.3122	$186.31	$186.30	$186.30
Purchase #6	$56.85	9.749%	$62.3923	$62.39	$62.40	$62.40
Purchase #7	$196.96	9.216%	$215.1118	$215.11	$215.10	$215.10
7 purchase totals =	$999.42		$1,085.9989	$1,085.99	$1,086.00	$1,086.00