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	$199.74	4.440%	$208.6085	$208.61	$208.60	$208.60
Purchase #2	$164.98	11.838%	$184.5103	$184.51	$184.50	$184.50
Purchase #3	$125.90	4.507%	$131.5743	$131.57	$131.55	$131.60
Purchase #4	$93.65	6.143%	$99.4029	$99.40	$99.40	$99.40
Purchase #5	$204.39	5.497%	$215.6253	$215.63	$215.65	$215.60
Purchase #6	$223.38	6.212%	$237.2564	$237.26	$237.25	$237.30
Purchase #7	$103.37	12.760%	$116.56	$116.56	$116.55	$116.60
7 purchase totals =	$1,115.41		$1,193.5377	$1,193.54	$1,193.50	$1,193.60