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	$118.47	7.867%	$127.79	$127.79	$127.80	$127.80
Purchase #2	$236.96	10.174%	$261.0683	$261.07	$261.05	$261.10
Purchase #3	$10.89	11.424%	$12.1341	$12.13	$12.15	$12.10
Purchase #4	$241.35	8.517%	$261.9058	$261.91	$261.90	$261.90
Purchase #5	$98.83	3.352%	$102.1428	$102.14	$102.15	$102.10
Purchase #6	$203.98	9.514%	$223.3867	$223.39	$223.40	$223.40
Purchase #7	$182.33	4.537%	$190.6023	$190.60	$190.60	$190.60
7 purchase totals =	$1,092.81		$1,179.0300	$1,179.03	$1,179.05	$1,179.00