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	$130.99	13.859%	$149.1439	$149.14	$149.15	$149.10
Purchase #2	$52.48	12.706%	$59.1481	$59.15	$59.15	$59.10
Purchase #3	$162.38	3.134%	$167.469	$167.47	$167.45	$167.50
Purchase #4	$133.90	12.159%	$150.1809	$150.18	$150.20	$150.20
Purchase #5	$225.68	6.541%	$240.4417	$240.44	$240.45	$240.40
Purchase #6	$151.70	13.353%	$171.9565	$171.96	$171.95	$172.00
Purchase #7	$76.44	9.276%	$83.5306	$83.53	$83.55	$83.50
7 purchase totals =	$933.57		$1,021.8707	$1,021.87	$1,021.90	$1,021.80