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	$119.86	6.696%	$127.8858	$127.89	$127.90	$127.90
Purchase #2	$207.96	7.184%	$222.8998	$222.90	$222.90	$222.90
Purchase #3	$211.53	10.359%	$233.4424	$233.44	$233.45	$233.40
Purchase #4	$23.90	7.224%	$25.6265	$25.63	$25.65	$25.60
Purchase #5	$53.86	3.693%	$55.849	$55.85	$55.85	$55.80
Purchase #6	$182.28	6.509%	$194.1446	$194.14	$194.15	$194.10
Purchase #7	$42.34	7.837%	$45.6582	$45.66	$45.65	$45.70
7 purchase totals =	$841.73		$905.5063	$905.51	$905.55	$905.40