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	$219.86	3.112%	$226.702	$226.70	$226.70	$226.70
Purchase #2	$9.47	6.807%	$10.1146	$10.11	$10.10	$10.10
Purchase #3	$179.62	9.326%	$196.3714	$196.37	$196.35	$196.40
Purchase #4	$119.42	6.770%	$127.5047	$127.50	$127.50	$127.50
Purchase #5	$63.41	7.146%	$67.9413	$67.94	$67.95	$67.90
Purchase #6	$167.33	9.558%	$183.3234	$183.32	$183.30	$183.30
Purchase #7	$29.32	8.596%	$31.8403	$31.84	$31.85	$31.80
7 purchase totals =	$788.43		$843.7977	$843.78	$843.75	$843.70