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	$100.64	13.262%	$113.9869	$113.99	$114.00	$114.00
Purchase #2	$53.59	11.721%	$59.8713	$59.87	$59.85	$59.90
Purchase #3	$37.66	10.203%	$41.5024	$41.50	$41.50	$41.50
Purchase #4	$211.27	7.237%	$226.5596	$226.56	$226.55	$226.60
Purchase #5	$250.39	9.262%	$273.5811	$273.58	$273.60	$273.60
Purchase #6	$144.49	4.393%	$150.8374	$150.84	$150.85	$150.80
Purchase #7	$102.71	5.192%	$108.0427	$108.04	$108.05	$108.00
7 purchase totals =	$900.75		$974.3814	$974.38	$974.40	$974.40