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	$179.55	8.274%	$194.406	$194.41	$194.40	$194.40
Purchase #2	$81.72	9.297%	$89.3175	$89.32	$89.30	$89.30
Purchase #3	$35.51	9.143%	$38.7567	$38.76	$38.75	$38.80
Purchase #4	$217.83	12.850%	$245.8212	$245.82	$245.80	$245.80
Purchase #5	$18.35	7.270%	$19.684	$19.68	$19.70	$19.70
Purchase #6	$121.47	4.733%	$127.2192	$127.22	$127.20	$127.20
Purchase #7	$103.68	8.389%	$112.3777	$112.38	$112.40	$112.40
7 purchase totals =	$758.11		$827.5823	$827.59	$827.55	$827.60