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	$164.89	5.671%	$174.2409	$174.24	$174.25	$174.20
Purchase #2	$59.28	7.342%	$63.6323	$63.63	$63.65	$63.60
Purchase #3	$224.94	12.727%	$253.5681	$253.57	$253.55	$253.60
Purchase #4	$17.50	12.498%	$19.6872	$19.69	$19.70	$19.70
Purchase #5	$126.64	3.873%	$131.5448	$131.54	$131.55	$131.50
Purchase #6	$60.56	9.874%	$66.5397	$66.54	$66.55	$66.50
Purchase #7	$53.83	6.270%	$57.2051	$57.21	$57.20	$57.20
7 purchase totals =	$707.64		$766.4181	$766.42	$766.45	$766.30