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	$104.98	7.426%	$112.7758	$112.78	$112.80	$112.80
Purchase #2	$121.46	5.211%	$127.7893	$127.79	$127.80	$127.80
Purchase #3	$39.33	11.540%	$43.8687	$43.87	$43.85	$43.90
Purchase #4	$89.45	11.432%	$99.6759	$99.68	$99.70	$99.70
Purchase #5	$155.34	13.447%	$176.2286	$176.23	$176.25	$176.20
Purchase #6	$113.45	11.847%	$126.8904	$126.89	$126.90	$126.90
Purchase #7	$28.36	5.555%	$29.9354	$29.94	$29.95	$29.90
7 purchase totals =	$652.37		$717.1641	$717.18	$717.25	$717.20