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	$107.51	3.759%	$111.5513	$111.55	$111.55	$111.60
Purchase #2	$160.41	9.405%	$175.4966	$175.50	$175.50	$175.50
Purchase #3	$40.25	13.802%	$45.8053	$45.81	$45.80	$45.80
Purchase #4	$216.49	4.582%	$226.4096	$226.41	$226.40	$226.40
Purchase #5	$106.57	3.534%	$110.3362	$110.34	$110.35	$110.30
Purchase #6	$250.79	13.402%	$284.4009	$284.40	$284.40	$284.40
Purchase #7	$167.42	3.749%	$173.6966	$173.70	$173.70	$173.70
7 purchase totals =	$1,049.44		$1,127.6965	$1,127.71	$1,127.70	$1,127.70