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	$22.90	10.131%	$25.22	$25.22	$25.20	$25.20
Purchase #2	$236.75	12.116%	$265.4346	$265.43	$265.45	$265.40
Purchase #3	$59.97	3.709%	$62.1943	$62.19	$62.20	$62.20
Purchase #4	$42.80	6.250%	$45.475	$45.48	$45.50	$45.50
Purchase #5	$186.95	8.852%	$203.4988	$203.50	$203.50	$203.50
Purchase #6	$52.73	12.678%	$59.4151	$59.42	$59.40	$59.40
Purchase #7	$104.83	6.571%	$111.7184	$111.72	$111.70	$111.70
7 purchase totals =	$706.93		$772.9562	$772.96	$772.95	$772.90