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	$90.89	6.831%	$97.0987	$97.10	$97.10	$97.10
Purchase #2	$83.36	3.757%	$86.4918	$86.49	$86.50	$86.50
Purchase #3	$56.39	6.174%	$59.8715	$59.87	$59.85	$59.90
Purchase #4	$5.71	3.818%	$5.928	$5.93	$5.95	$5.90
Purchase #5	$63.90	8.715%	$69.4689	$69.47	$69.45	$69.50
Purchase #6	$109.33	3.609%	$113.2757	$113.28	$113.30	$113.30
Purchase #7	$191.74	10.752%	$212.3559	$212.36	$212.35	$212.40
7 purchase totals =	$601.32		$644.4905	$644.50	$644.50	$644.60