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	$114.50	3.786%	$118.835	$118.84	$118.85	$118.80
Purchase #2	$47.53	13.709%	$54.0459	$54.05	$54.05	$54.00
Purchase #3	$59.25	3.373%	$61.2485	$61.25	$61.25	$61.20
Purchase #4	$10.78	4.802%	$11.2977	$11.30	$11.30	$11.30
Purchase #5	$161.25	11.567%	$179.9018	$179.90	$179.90	$179.90
Purchase #6	$169.56	10.352%	$187.1129	$187.11	$187.10	$187.10
Purchase #7	$151.63	8.739%	$164.8809	$164.88	$164.90	$164.90
7 purchase totals =	$714.50		$777.3227	$777.33	$777.35	$777.20