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	$179.76	3.441%	$185.9455	$185.95	$185.95	$185.90
Purchase #2	$203.26	7.693%	$218.8968	$218.90	$218.90	$218.90
Purchase #3	$190.34	5.407%	$200.6317	$200.63	$200.65	$200.60
Purchase #4	$143.68	12.753%	$162.0035	$162.00	$162.00	$162.00
Purchase #5	$147.27	3.240%	$152.0415	$152.04	$152.05	$152.00
Purchase #6	$204.77	13.120%	$231.6358	$231.64	$231.65	$231.60
Purchase #7	$126.64	10.116%	$139.4509	$139.45	$139.45	$139.50
7 purchase totals =	$1,195.72		$1,290.6057	$1,290.61	$1,290.65	$1,290.50