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	$199.56	10.387%	$220.2883	$220.29	$220.30	$220.30
Purchase #2	$155.98	5.684%	$164.8459	$164.85	$164.85	$164.80
Purchase #3	$119.40	6.563%	$127.2362	$127.24	$127.25	$127.20
Purchase #4	$56.32	4.691%	$58.962	$58.96	$58.95	$59.00
Purchase #5	$154.34	4.138%	$160.7266	$160.73	$160.75	$160.70
Purchase #6	$147.29	6.337%	$156.6238	$156.62	$156.60	$156.60
Purchase #7	$158.42	12.266%	$177.8518	$177.85	$177.85	$177.90
7 purchase totals =	$991.31		$1,066.5346	$1,066.54	$1,066.55	$1,066.50