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	$135.47	12.461%	$152.3509	$152.35	$152.35	$152.40
Purchase #2	$35.47	5.356%	$37.3698	$37.37	$37.35	$37.40
Purchase #3	$158.84	6.184%	$168.6627	$168.66	$168.65	$168.70
Purchase #4	$191.85	4.297%	$200.0938	$200.09	$200.10	$200.10
Purchase #5	$234.68	11.780%	$262.3253	$262.33	$262.35	$262.30
Purchase #6	$227.47	12.248%	$255.3305	$255.33	$255.35	$255.30
Purchase #7	$45.71	11.835%	$51.1198	$51.12	$51.10	$51.10
7 purchase totals =	$1,029.49		$1,127.2528	$1,127.25	$1,127.25	$1,127.30