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	$195.27	10.502%	$215.7773	$215.78	$215.80	$215.80
Purchase #2	$136.46	10.142%	$150.2998	$150.30	$150.30	$150.30
Purchase #3	$200.66	4.807%	$210.3057	$210.31	$210.30	$210.30
Purchase #4	$80.95	8.558%	$87.8777	$87.88	$87.90	$87.90
Purchase #5	$44.76	3.587%	$46.3655	$46.37	$46.35	$46.40
Purchase #6	$87.80	11.145%	$97.5853	$97.59	$97.60	$97.60
Purchase #7	$86.89	3.354%	$89.8043	$89.80	$89.80	$89.80
7 purchase totals =	$832.79		$898.0156	$898.03	$898.05	$898.10