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	$129.64	4.560%	$135.5516	$135.55	$135.55	$135.60
Purchase #2	$141.28	6.771%	$150.8461	$150.85	$150.85	$150.80
Purchase #3	$52.53	12.575%	$59.1356	$59.14	$59.15	$59.10
Purchase #4	$153.34	4.472%	$160.1974	$160.20	$160.20	$160.20
Purchase #5	$82.93	9.213%	$90.5703	$90.57	$90.55	$90.60
Purchase #6	$139.67	5.174%	$146.8965	$146.90	$146.90	$146.90
Purchase #7	$150.90	7.614%	$162.3895	$162.39	$162.40	$162.40
7 purchase totals =	$850.29		$905.5870	$905.60	$905.60	$905.60