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	$105.35	6.233%	$111.9165	$111.92	$111.90	$111.90
Purchase #2	$35.51	5.775%	$37.5607	$37.56	$37.55	$37.60
Purchase #3	$64.42	10.367%	$71.0984	$71.10	$71.10	$71.10
Purchase #4	$168.76	10.453%	$186.4005	$186.40	$186.40	$186.40
Purchase #5	$75.45	12.536%	$84.9084	$84.91	$84.90	$84.90
Purchase #6	$109.91	3.143%	$113.3645	$113.36	$113.35	$113.40
Purchase #7	$113.54	9.874%	$124.7509	$124.75	$124.75	$124.80
7 purchase totals =	$672.94		$729.9999	$730.00	$729.95	$730.10