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	$138.85	3.160%	$143.2377	$143.24	$143.25	$143.20
Purchase #2	$191.80	4.498%	$200.4272	$200.43	$200.45	$200.40
Purchase #3	$237.44	4.401%	$247.8897	$247.89	$247.90	$247.90
Purchase #4	$49.83	8.806%	$54.218	$54.22	$54.20	$54.20
Purchase #5	$172.76	13.112%	$195.4123	$195.41	$195.40	$195.40
Purchase #6	$79.25	10.118%	$87.2685	$87.27	$87.25	$87.30
Purchase #7	$186.64	7.452%	$200.5484	$200.55	$200.55	$200.50
7 purchase totals =	$1,056.57		$1,129.0018	$1,129.01	$1,129.00	$1,128.90