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	$106.59	10.162%	$117.4217	$117.42	$117.40	$117.40
Purchase #2	$53.34	11.225%	$59.3274	$59.33	$59.35	$59.30
Purchase #3	$215.92	7.342%	$231.7728	$231.77	$231.75	$231.80
Purchase #4	$179.84	10.591%	$198.8869	$198.89	$198.90	$198.90
Purchase #5	$201.51	5.277%	$212.1437	$212.14	$212.15	$212.10
Purchase #6	$171.36	4.779%	$179.5493	$179.55	$179.55	$179.50
Purchase #7	$172.90	13.276%	$195.8542	$195.85	$195.85	$195.90
7 purchase totals =	$1,101.46		$1,194.9560	$1,194.95	$1,194.95	$1,194.90