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	$182.69	7.709%	$196.7736	$196.77	$196.75	$196.80
Purchase #2	$194.70	12.589%	$219.2108	$219.21	$219.20	$219.20
Purchase #3	$99.36	10.585%	$109.8773	$109.88	$109.90	$109.90
Purchase #4	$49.78	4.182%	$51.8618	$51.86	$51.85	$51.90
Purchase #5	$65.93	9.733%	$72.347	$72.35	$72.35	$72.30
Purchase #6	$51.50	10.363%	$56.8369	$56.84	$56.85	$56.80
Purchase #7	$232.80	11.116%	$258.678	$258.68	$258.70	$258.70
7 purchase totals =	$876.76		$965.5854	$965.59	$965.60	$965.60