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	$131.81	11.305%	$146.7111	$146.71	$146.70	$146.70
Purchase #2	$78.26	7.232%	$83.9198	$83.92	$83.90	$83.90
Purchase #3	$79.58	3.272%	$82.1839	$82.18	$82.20	$82.20
Purchase #4	$20.82	6.642%	$22.2029	$22.20	$22.20	$22.20
Purchase #5	$189.65	3.802%	$196.8605	$196.86	$196.85	$196.90
Purchase #6	$245.78	5.641%	$259.6444	$259.64	$259.65	$259.60
Purchase #7	$126.88	5.844%	$134.2949	$134.29	$134.30	$134.30
7 purchase totals =	$872.78		$925.8175	$925.80	$925.80	$925.80