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	$36.48	3.259%	$37.6689	$37.67	$37.65	$37.70
Purchase #2	$11.56	3.735%	$11.9918	$11.99	$12.00	$12.00
Purchase #3	$243.78	10.120%	$268.4505	$268.45	$268.45	$268.50
Purchase #4	$116.88	12.334%	$131.296	$131.30	$131.30	$131.30
Purchase #5	$92.35	11.649%	$103.1079	$103.11	$103.10	$103.10
Purchase #6	$14.47	9.733%	$15.8784	$15.88	$15.90	$15.90
Purchase #7	$39.26	11.553%	$43.7957	$43.80	$43.80	$43.80
7 purchase totals =	$554.78		$612.1892	$612.20	$612.20	$612.30