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	$219.94	10.477%	$242.9831	$242.98	$243.00	$243.00
Purchase #2	$230.55	5.476%	$243.1749	$243.17	$243.15	$243.20
Purchase #3	$81.62	11.314%	$90.8545	$90.85	$90.85	$90.90
Purchase #4	$127.42	7.861%	$137.4365	$137.44	$137.45	$137.40
Purchase #5	$148.86	9.434%	$162.9035	$162.90	$162.90	$162.90
Purchase #6	$102.77	9.209%	$112.2341	$112.23	$112.25	$112.20
Purchase #7	$250.55	12.351%	$281.4954	$281.50	$281.50	$281.50
7 purchase totals =	$1,161.71		$1,271.0820	$1,271.07	$1,271.10	$1,271.10