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	$67.54	6.365%	$71.8389	$71.84	$71.85	$71.80
Purchase #2	$211.62	7.219%	$226.8968	$226.90	$226.90	$226.90
Purchase #3	$6.82	5.220%	$7.176	$7.18	$7.20	$7.20
Purchase #4	$92.51	11.210%	$102.8804	$102.88	$102.90	$102.90
Purchase #5	$53.25	8.179%	$57.6053	$57.61	$57.60	$57.60
Purchase #6	$57.34	3.443%	$59.3142	$59.31	$59.30	$59.30
Purchase #7	$95.40	3.215%	$98.4671	$98.47	$98.45	$98.50
7 purchase totals =	$584.48		$624.1787	$624.19	$624.20	$624.20