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	$161.39	6.844%	$172.4355	$172.44	$172.45	$172.40
Purchase #2	$250.80	9.154%	$273.7582	$273.76	$273.75	$273.80
Purchase #3	$59.88	7.652%	$64.462	$64.46	$64.45	$64.50
Purchase #4	$161.54	12.595%	$181.886	$181.89	$181.90	$181.90
Purchase #5	$215.54	7.207%	$231.074	$231.07	$231.05	$231.10
Purchase #6	$57.84	6.119%	$61.3792	$61.38	$61.40	$61.40
Purchase #7	$145.46	3.734%	$150.8915	$150.89	$150.90	$150.90
7 purchase totals =	$1,052.45		$1,135.8864	$1,135.89	$1,135.90	$1,136.00