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	$151.50	3.634%	$157.0055	$157.01	$157.00	$157.00
Purchase #2	$88.63	3.811%	$92.0077	$92.01	$92.00	$92.00
Purchase #3	$99.75	3.213%	$102.955	$102.96	$102.95	$103.00
Purchase #4	$138.73	8.492%	$150.511	$150.51	$150.50	$150.50
Purchase #5	$143.96	8.771%	$156.5867	$156.59	$156.60	$156.60
Purchase #6	$134.89	12.337%	$151.5314	$151.53	$151.55	$151.50
Purchase #7	$24.29	4.569%	$25.3998	$25.40	$25.40	$25.40
7 purchase totals =	$781.75		$835.9971	$836.01	$836.00	$836.00