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	$112.87	4.541%	$117.9954	$118.00	$118.00	$118.00
Purchase #2	$80.83	11.260%	$89.9315	$89.93	$89.95	$89.90
Purchase #3	$23.72	5.549%	$25.0362	$25.04	$25.05	$25.00
Purchase #4	$62.80	13.607%	$71.3452	$71.35	$71.35	$71.30
Purchase #5	$248.83	7.667%	$267.9078	$267.91	$267.90	$267.90
Purchase #6	$134.68	13.123%	$152.3541	$152.35	$152.35	$152.40
Purchase #7	$200.61	5.432%	$211.5071	$211.51	$211.50	$211.50
7 purchase totals =	$864.34		$936.0773	$936.09	$936.10	$936.00