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	$157.48	10.678%	$174.2957	$174.30	$174.30	$174.30
Purchase #2	$245.39	4.116%	$255.4903	$255.49	$255.50	$255.50
Purchase #3	$196.30	6.215%	$208.5	$208.50	$208.50	$208.50
Purchase #4	$113.71	12.494%	$127.9169	$127.92	$127.90	$127.90
Purchase #5	$179.46	6.345%	$190.8467	$190.85	$190.85	$190.80
Purchase #6	$33.51	13.161%	$37.9203	$37.92	$37.90	$37.90
Purchase #7	$7.37	9.481%	$8.0687	$8.07	$8.05	$8.10
7 purchase totals =	$933.22		$1,003.0386	$1,003.05	$1,003.00	$1,003.00