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	$112.88	12.418%	$126.8974	$126.90	$126.90	$126.90
Purchase #2	$167.32	4.437%	$174.744	$174.74	$174.75	$174.70
Purchase #3	$127.27	12.781%	$143.5364	$143.54	$143.55	$143.50
Purchase #4	$138.32	4.375%	$144.3715	$144.37	$144.35	$144.40
Purchase #5	$222.28	9.217%	$242.7675	$242.77	$242.75	$242.80
Purchase #6	$162.33	3.765%	$168.4417	$168.44	$168.45	$168.40
Purchase #7	$227.45	12.488%	$255.854	$255.85	$255.85	$255.90
7 purchase totals =	$1,157.85		$1,256.6125	$1,256.61	$1,256.60	$1,256.60