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	$36.80	9.394%	$40.257	$40.26	$40.25	$40.30
Purchase #2	$20.26	7.453%	$21.77	$21.77	$21.75	$21.80
Purchase #3	$219.54	8.616%	$238.4556	$238.46	$238.45	$238.50
Purchase #4	$250.57	13.757%	$285.0409	$285.04	$285.05	$285.00
Purchase #5	$83.87	8.355%	$90.8773	$90.88	$90.90	$90.90
Purchase #6	$244.29	9.359%	$267.1531	$267.15	$267.15	$267.20
Purchase #7	$240.77	10.382%	$265.7667	$265.77	$265.75	$265.80
7 purchase totals =	$1,096.10		$1,209.3206	$1,209.33	$1,209.30	$1,209.50