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	$218.81	5.534%	$230.9189	$230.92	$230.90	$230.90
Purchase #2	$43.94	4.347%	$45.8501	$45.85	$45.85	$45.90
Purchase #3	$56.38	13.796%	$64.1582	$64.16	$64.15	$64.20
Purchase #4	$135.73	12.743%	$153.0261	$153.03	$153.05	$153.00
Purchase #5	$99.84	12.468%	$112.2881	$112.29	$112.30	$112.30
Purchase #6	$71.99	9.229%	$78.634	$78.63	$78.65	$78.60
Purchase #7	$31.75	11.508%	$35.4038	$35.40	$35.40	$35.40
7 purchase totals =	$658.44		$720.2792	$720.28	$720.30	$720.30