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	$167.54	11.359%	$186.5709	$186.57	$186.55	$186.60
Purchase #2	$38.67	12.212%	$43.3924	$43.39	$43.40	$43.40
Purchase #3	$84.69	13.191%	$95.8615	$95.86	$95.85	$95.90
Purchase #4	$77.50	5.166%	$81.5037	$81.50	$81.50	$81.50
Purchase #5	$38.46	6.480%	$40.9522	$40.95	$40.95	$41.00
Purchase #6	$51.50	4.187%	$53.6563	$53.66	$53.65	$53.70
Purchase #7	$230.25	8.672%	$250.2173	$250.22	$250.20	$250.20
7 purchase totals =	$688.61		$752.1543	$752.15	$752.10	$752.30