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	$102.78	11.786%	$114.8937	$114.89	$114.90	$114.90
Purchase #2	$142.69	6.687%	$152.2317	$152.23	$152.25	$152.20
Purchase #3	$25.63	12.685%	$28.8812	$28.88	$28.90	$28.90
Purchase #4	$16.92	6.504%	$18.0205	$18.02	$18.00	$18.00
Purchase #5	$223.31	3.291%	$230.6591	$230.66	$230.65	$230.70
Purchase #6	$216.44	6.649%	$230.8311	$230.83	$230.85	$230.80
Purchase #7	$243.86	11.353%	$271.5454	$271.55	$271.55	$271.50
7 purchase totals =	$971.63		$1,047.0627	$1,047.06	$1,047.10	$1,047.00