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	$50.66	5.674%	$53.5344	$53.53	$53.55	$53.50
Purchase #2	$38.96	3.672%	$40.3906	$40.39	$40.40	$40.40
Purchase #3	$179.88	5.440%	$189.6655	$189.67	$189.65	$189.70
Purchase #4	$119.93	7.630%	$129.0807	$129.08	$129.10	$129.10
Purchase #5	$168.28	11.277%	$187.2569	$187.26	$187.25	$187.30
Purchase #6	$123.75	6.116%	$131.3186	$131.32	$131.30	$131.30
Purchase #7	$180.77	5.172%	$190.1194	$190.12	$190.10	$190.10
7 purchase totals =	$862.23		$921.3661	$921.37	$921.35	$921.40