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	$186.75	10.334%	$206.0487	$206.05	$206.05	$206.00
Purchase #2	$80.61	10.680%	$89.2191	$89.22	$89.20	$89.20
Purchase #3	$183.40	3.720%	$190.2225	$190.22	$190.20	$190.20
Purchase #4	$124.51	6.334%	$132.3965	$132.40	$132.40	$132.40
Purchase #5	$195.64	10.731%	$216.6341	$216.63	$216.65	$216.60
Purchase #6	$38.31	7.611%	$41.2258	$41.23	$41.25	$41.20
Purchase #7	$232.94	9.846%	$255.8753	$255.88	$255.90	$255.90
7 purchase totals =	$1,042.16		$1,131.6220	$1,131.63	$1,131.65	$1,131.50