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	$179.60	7.200%	$192.5312	$192.53	$192.55	$192.50
Purchase #2	$59.73	13.299%	$67.6735	$67.67	$67.65	$67.70
Purchase #3	$164.52	11.498%	$183.4365	$183.44	$183.45	$183.40
Purchase #4	$42.74	5.613%	$45.139	$45.14	$45.15	$45.10
Purchase #5	$78.57	11.144%	$87.3258	$87.33	$87.35	$87.30
Purchase #6	$216.35	3.780%	$224.528	$224.53	$224.55	$224.50
Purchase #7	$217.93	13.421%	$247.1784	$247.18	$247.20	$247.20
7 purchase totals =	$959.44		$1,047.8124	$1,047.82	$1,047.90	$1,047.70