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	$172.44	7.287%	$185.0057	$185.01	$185.00	$185.00
Purchase #2	$71.70	12.377%	$80.5743	$80.57	$80.55	$80.60
Purchase #3	$69.49	4.434%	$72.5712	$72.57	$72.55	$72.60
Purchase #4	$167.96	8.720%	$182.6061	$182.61	$182.60	$182.60
Purchase #5	$30.36	4.224%	$31.6424	$31.64	$31.65	$31.60
Purchase #6	$231.79	8.184%	$250.7597	$250.76	$250.75	$250.80
Purchase #7	$227.88	7.228%	$244.3512	$244.35	$244.35	$244.40
7 purchase totals =	$971.62		$1,047.5106	$1,047.51	$1,047.45	$1,047.60