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	$143.96	5.757%	$152.2478	$152.25	$152.25	$152.20
Purchase #2	$114.67	4.576%	$119.9173	$119.92	$119.90	$119.90
Purchase #3	$147.73	8.618%	$160.4614	$160.46	$160.45	$160.50
Purchase #4	$236.27	8.253%	$255.7694	$255.77	$255.75	$255.80
Purchase #5	$200.93	5.579%	$212.1399	$212.14	$212.15	$212.10
Purchase #6	$146.39	6.610%	$156.0664	$156.07	$156.05	$156.10
Purchase #7	$31.78	7.509%	$34.1664	$34.17	$34.15	$34.20
7 purchase totals =	$1,021.73		$1,090.7686	$1,090.78	$1,090.70	$1,090.80