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	$101.78	12.659%	$114.6643	$114.66	$114.65	$114.70
Purchase #2	$165.47	10.390%	$182.6623	$182.66	$182.65	$182.70
Purchase #3	$63.57	11.201%	$70.6905	$70.69	$70.70	$70.70
Purchase #4	$126.54	3.739%	$131.2713	$131.27	$131.25	$131.30
Purchase #5	$159.80	3.236%	$164.9711	$164.97	$164.95	$165.00
Purchase #6	$155.26	6.127%	$164.7728	$164.77	$164.75	$164.80
Purchase #7	$61.96	13.453%	$70.2955	$70.30	$70.30	$70.30
7 purchase totals =	$834.38		$899.3278	$899.32	$899.25	$899.50