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	$63.85	12.328%	$71.7214	$71.72	$71.70	$71.70
Purchase #2	$12.46	5.539%	$13.1502	$13.15	$13.15	$13.20
Purchase #3	$156.73	7.736%	$168.8546	$168.85	$168.85	$168.90
Purchase #4	$13.86	7.673%	$14.9235	$14.92	$14.90	$14.90
Purchase #5	$39.99	9.359%	$43.7327	$43.73	$43.75	$43.70
Purchase #6	$215.55	7.589%	$231.9081	$231.91	$231.90	$231.90
Purchase #7	$175.57	5.563%	$185.337	$185.34	$185.35	$185.30
7 purchase totals =	$678.01		$729.6275	$729.62	$729.60	$729.60