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	$107.82	4.199%	$112.3474	$112.35	$112.35	$112.30
Purchase #2	$138.43	3.414%	$143.156	$143.16	$143.15	$143.20
Purchase #3	$176.39	11.407%	$196.5108	$196.51	$196.50	$196.50
Purchase #4	$190.53	9.539%	$208.7047	$208.70	$208.70	$208.70
Purchase #5	$164.94	7.251%	$176.8998	$176.90	$176.90	$176.90
Purchase #6	$21.62	6.437%	$23.0117	$23.01	$23.00	$23.00
Purchase #7	$209.60	11.538%	$233.7836	$233.78	$233.80	$233.80
7 purchase totals =	$1,009.33		$1,094.4140	$1,094.41	$1,094.40	$1,094.40