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	$198.83	12.226%	$223.139	$223.14	$223.15	$223.10
Purchase #2	$228.41	12.215%	$256.3103	$256.31	$256.30	$256.30
Purchase #3	$96.77	5.183%	$101.7856	$101.79	$101.80	$101.80
Purchase #4	$153.46	7.245%	$164.5782	$164.58	$164.60	$164.60
Purchase #5	$161.38	5.327%	$169.9767	$169.98	$170.00	$170.00
Purchase #6	$80.66	12.281%	$90.5659	$90.57	$90.55	$90.60
Purchase #7	$170.81	11.129%	$189.8194	$189.82	$189.80	$189.80
7 purchase totals =	$1,090.32		$1,196.1751	$1,196.19	$1,196.20	$1,196.20