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	$134.42	3.764%	$139.4796	$139.48	$139.50	$139.50
Purchase #2	$177.73	10.756%	$196.8466	$196.85	$196.85	$196.80
Purchase #3	$145.49	3.356%	$150.3726	$150.37	$150.35	$150.40
Purchase #4	$104.34	9.396%	$114.1438	$114.14	$114.15	$114.10
Purchase #5	$202.81	8.675%	$220.4038	$220.40	$220.40	$220.40
Purchase #6	$125.26	11.450%	$139.6023	$139.60	$139.60	$139.60
Purchase #7	$72.85	13.765%	$82.8778	$82.88	$82.90	$82.90
7 purchase totals =	$962.90		$1,043.7265	$1,043.72	$1,043.75	$1,043.70