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	$65.75	10.740%	$72.8116	$72.81	$72.80	$72.80
Purchase #2	$186.72	10.799%	$206.8839	$206.88	$206.90	$206.90
Purchase #3	$57.44	3.265%	$59.3154	$59.32	$59.30	$59.30
Purchase #4	$137.49	5.839%	$145.518	$145.52	$145.50	$145.50
Purchase #5	$143.93	8.725%	$156.4879	$156.49	$156.50	$156.50
Purchase #6	$161.76	4.356%	$168.8063	$168.81	$168.80	$168.80
Purchase #7	$234.80	10.330%	$259.0548	$259.05	$259.05	$259.10
7 purchase totals =	$987.89		$1,068.8779	$1,068.88	$1,068.85	$1,068.90