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	$42.47	8.218%	$45.9602	$45.96	$45.95	$46.00
Purchase #2	$234.46	12.712%	$264.2646	$264.26	$264.25	$264.30
Purchase #3	$197.93	10.535%	$218.7819	$218.78	$218.80	$218.80
Purchase #4	$215.30	5.104%	$226.2889	$226.29	$226.30	$226.30
Purchase #5	$47.69	7.645%	$51.3359	$51.34	$51.35	$51.30
Purchase #6	$73.39	12.314%	$82.4272	$82.43	$82.45	$82.40
Purchase #7	$135.97	6.134%	$144.3104	$144.31	$144.30	$144.30
7 purchase totals =	$947.21		$1,033.3691	$1,033.37	$1,033.40	$1,033.40