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	$106.35	11.111%	$118.1665	$118.17	$118.15	$118.20
Purchase #2	$86.42	13.313%	$97.9251	$97.93	$97.95	$97.90
Purchase #3	$88.42	9.746%	$97.0374	$97.04	$97.05	$97.00
Purchase #4	$228.53	9.123%	$249.3788	$249.38	$249.40	$249.40
Purchase #5	$101.67	9.294%	$111.1192	$111.12	$111.10	$111.10
Purchase #6	$225.85	10.705%	$250.0272	$250.03	$250.05	$250.00
Purchase #7	$153.77	7.665%	$165.5565	$165.56	$165.55	$165.60
7 purchase totals =	$991.01		$1,089.2107	$1,089.23	$1,089.25	$1,089.20