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	$68.25	4.189%	$71.109	$71.11	$71.10	$71.10
Purchase #2	$60.90	8.272%	$65.9376	$65.94	$65.95	$65.90
Purchase #3	$122.56	3.528%	$126.8839	$126.88	$126.90	$126.90
Purchase #4	$224.49	8.437%	$243.4302	$243.43	$243.45	$243.40
Purchase #5	$188.85	10.299%	$208.2997	$208.30	$208.30	$208.30
Purchase #6	$46.47	4.676%	$48.6429	$48.64	$48.65	$48.60
Purchase #7	$79.89	11.518%	$89.0917	$89.09	$89.10	$89.10
7 purchase totals =	$791.41		$853.3950	$853.39	$853.45	$853.30