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	$169.32	10.357%	$186.8565	$186.86	$186.85	$186.90
Purchase #2	$182.80	11.861%	$204.4819	$204.48	$204.50	$204.50
Purchase #3	$229.37	12.661%	$258.4105	$258.41	$258.40	$258.40
Purchase #4	$20.58	4.489%	$21.5038	$21.50	$21.50	$21.50
Purchase #5	$41.25	13.720%	$46.9095	$46.91	$46.90	$46.90
Purchase #6	$97.77	6.381%	$104.0087	$104.01	$104.00	$104.00
Purchase #7	$99.64	10.196%	$109.7993	$109.80	$109.80	$109.80
7 purchase totals =	$840.73		$931.9702	$931.97	$931.95	$932.00