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	$43.50	12.780%	$49.0593	$49.06	$49.05	$49.10
Purchase #2	$224.70	4.314%	$234.3936	$234.39	$234.40	$234.40
Purchase #3	$64.45	11.515%	$71.8714	$71.87	$71.85	$71.90
Purchase #4	$127.43	3.289%	$131.6212	$131.62	$131.60	$131.60
Purchase #5	$57.25	11.593%	$63.887	$63.89	$63.90	$63.90
Purchase #6	$89.41	13.851%	$101.7942	$101.79	$101.80	$101.80
Purchase #7	$244.88	8.116%	$264.7545	$264.75	$264.75	$264.80
7 purchase totals =	$851.62		$917.3812	$917.37	$917.35	$917.50