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	$114.92	10.619%	$127.1234	$127.12	$127.10	$127.10
Purchase #2	$113.41	12.114%	$127.1485	$127.15	$127.15	$127.10
Purchase #3	$229.97	6.437%	$244.7732	$244.77	$244.75	$244.80
Purchase #4	$13.29	8.277%	$14.39	$14.39	$14.40	$14.40
Purchase #5	$35.54	3.615%	$36.8248	$36.82	$36.80	$36.80
Purchase #6	$55.67	5.465%	$58.7124	$58.71	$58.70	$58.70
Purchase #7	$89.37	12.707%	$100.7262	$100.73	$100.75	$100.70
7 purchase totals =	$652.17		$709.6985	$709.69	$709.65	$709.60