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	$126.83	11.172%	$140.9994	$141.00	$141.00	$141.00
Purchase #2	$119.88	6.254%	$127.3773	$127.38	$127.40	$127.40
Purchase #3	$220.97	10.625%	$244.4481	$244.45	$244.45	$244.40
Purchase #4	$149.56	5.800%	$158.2345	$158.23	$158.25	$158.20
Purchase #5	$39.72	11.447%	$44.2667	$44.27	$44.25	$44.30
Purchase #6	$193.35	8.695%	$210.1618	$210.16	$210.15	$210.20
Purchase #7	$161.66	6.865%	$172.758	$172.76	$172.75	$172.80
7 purchase totals =	$1,011.97		$1,098.2458	$1,098.25	$1,098.25	$1,098.30