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	$237.81	8.360%	$257.6909	$257.69	$257.70	$257.70
Purchase #2	$169.25	13.365%	$191.8703	$191.87	$191.85	$191.90
Purchase #3	$118.46	11.325%	$131.8756	$131.88	$131.90	$131.90
Purchase #4	$90.41	7.126%	$96.8526	$96.85	$96.85	$96.90
Purchase #5	$39.85	6.797%	$42.5586	$42.56	$42.55	$42.60
Purchase #6	$174.86	13.785%	$198.9645	$198.96	$198.95	$199.00
Purchase #7	$84.61	9.138%	$92.3417	$92.34	$92.35	$92.30
7 purchase totals =	$915.25		$1,012.1542	$1,012.15	$1,012.15	$1,012.30