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	$131.27	7.232%	$140.7634	$140.76	$140.75	$140.80
Purchase #2	$158.99	7.726%	$171.2736	$171.27	$171.25	$171.30
Purchase #3	$78.30	3.168%	$80.7805	$80.78	$80.80	$80.80
Purchase #4	$97.72	3.150%	$100.7982	$100.80	$100.80	$100.80
Purchase #5	$187.83	12.553%	$211.4083	$211.41	$211.40	$211.40
Purchase #6	$187.89	4.225%	$195.8284	$195.83	$195.85	$195.80
Purchase #7	$161.92	4.868%	$169.8023	$169.80	$169.80	$169.80
7 purchase totals =	$1,003.92		$1,070.6547	$1,070.65	$1,070.65	$1,070.70