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	$62.27	8.434%	$67.5219	$67.52	$67.50	$67.50
Purchase #2	$220.86	13.470%	$250.6098	$250.61	$250.60	$250.60
Purchase #3	$86.96	4.398%	$90.7845	$90.78	$90.80	$90.80
Purchase #4	$171.27	7.229%	$183.6511	$183.65	$183.65	$183.70
Purchase #5	$157.86	4.170%	$164.4428	$164.44	$164.45	$164.40
Purchase #6	$242.30	3.291%	$250.2741	$250.27	$250.25	$250.30
Purchase #7	$226.60	8.320%	$245.4531	$245.45	$245.45	$245.50
7 purchase totals =	$1,168.12		$1,252.7373	$1,252.72	$1,252.70	$1,252.80