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	$229.29	13.666%	$260.6248	$260.62	$260.60	$260.60
Purchase #2	$52.80	13.279%	$59.8113	$59.81	$59.80	$59.80
Purchase #3	$173.31	11.768%	$193.7051	$193.71	$193.70	$193.70
Purchase #4	$176.36	11.656%	$196.9165	$196.92	$196.90	$196.90
Purchase #5	$12.64	7.205%	$13.5507	$13.55	$13.55	$13.60
Purchase #6	$90.84	12.173%	$101.898	$101.90	$101.90	$101.90
Purchase #7	$109.58	4.233%	$114.2185	$114.22	$114.20	$114.20
7 purchase totals =	$844.82		$940.7249	$940.73	$940.65	$940.70