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	$129.35	8.580%	$140.4482	$140.45	$140.45	$140.40
Purchase #2	$89.37	3.300%	$92.3192	$92.32	$92.30	$92.30
Purchase #3	$159.66	9.776%	$175.2684	$175.27	$175.25	$175.30
Purchase #4	$145.39	12.854%	$164.0784	$164.08	$164.10	$164.10
Purchase #5	$134.36	5.180%	$141.3198	$141.32	$141.30	$141.30
Purchase #6	$158.27	3.662%	$164.0658	$164.07	$164.05	$164.10
Purchase #7	$248.94	12.263%	$279.4675	$279.47	$279.45	$279.50
7 purchase totals =	$1,065.34		$1,156.9673	$1,156.98	$1,156.90	$1,157.00