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	$165.73	5.638%	$175.0739	$175.07	$175.05	$175.10
Purchase #2	$42.45	4.627%	$44.4142	$44.41	$44.40	$44.40
Purchase #3	$35.54	11.212%	$39.5247	$39.52	$39.50	$39.50
Purchase #4	$41.57	7.140%	$44.5381	$44.54	$44.55	$44.50
Purchase #5	$132.49	9.690%	$145.3283	$145.33	$145.35	$145.30
Purchase #6	$53.56	7.460%	$57.5556	$57.56	$57.55	$57.60
Purchase #7	$87.59	3.379%	$90.5497	$90.55	$90.55	$90.50
7 purchase totals =	$558.93		$596.9845	$596.98	$596.95	$596.90