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	$221.70	3.444%	$229.3353	$229.34	$229.35	$229.30
Purchase #2	$150.51	5.269%	$158.4404	$158.44	$158.45	$158.40
Purchase #3	$61.46	3.641%	$63.6978	$63.70	$63.70	$63.70
Purchase #4	$33.39	7.683%	$35.9554	$35.96	$35.95	$36.00
Purchase #5	$53.39	11.673%	$59.6222	$59.62	$59.60	$59.60
Purchase #6	$106.92	11.398%	$119.1067	$119.11	$119.10	$119.10
Purchase #7	$92.76	8.738%	$100.8654	$100.87	$100.85	$100.90
7 purchase totals =	$720.13		$767.0232	$767.04	$767.00	$767.00