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	$191.89	8.799%	$208.7744	$208.77	$208.75	$208.80
Purchase #2	$33.87	10.782%	$37.5219	$37.52	$37.50	$37.50
Purchase #3	$141.39	7.738%	$152.3308	$152.33	$152.35	$152.30
Purchase #4	$132.99	6.264%	$141.3205	$141.32	$141.30	$141.30
Purchase #5	$109.72	6.545%	$116.9012	$116.90	$116.90	$116.90
Purchase #6	$122.46	11.149%	$136.1131	$136.11	$136.10	$136.10
Purchase #7	$223.57	4.678%	$234.0286	$234.03	$234.05	$234.00
7 purchase totals =	$955.89		$1,026.9905	$1,026.98	$1,026.95	$1,026.90