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	$61.91	8.606%	$67.238	$67.24	$67.25	$67.20
Purchase #2	$127.73	12.165%	$143.2684	$143.27	$143.25	$143.30
Purchase #3	$113.80	11.752%	$127.1738	$127.17	$127.15	$127.20
Purchase #4	$67.28	9.626%	$73.7564	$73.76	$73.75	$73.80
Purchase #5	$67.81	13.735%	$77.1237	$77.12	$77.10	$77.10
Purchase #6	$163.66	10.711%	$181.1896	$181.19	$181.20	$181.20
Purchase #7	$13.35	12.538%	$15.0238	$15.02	$15.00	$15.00
7 purchase totals =	$615.54		$684.7737	$684.77	$684.70	$684.80