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	$132.47	11.134%	$147.2192	$147.22	$147.20	$147.20
Purchase #2	$159.53	9.135%	$174.1031	$174.10	$174.10	$174.10
Purchase #3	$243.83	11.314%	$271.4169	$271.42	$271.40	$271.40
Purchase #4	$171.69	4.222%	$178.9388	$178.94	$178.95	$178.90
Purchase #5	$206.75	4.293%	$215.6258	$215.63	$215.65	$215.60
Purchase #6	$46.83	6.598%	$49.9198	$49.92	$49.90	$49.90
Purchase #7	$40.86	11.234%	$45.4502	$45.45	$45.45	$45.50
7 purchase totals =	$1,001.96		$1,082.6738	$1,082.68	$1,082.65	$1,082.60