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	$236.50	10.689%	$261.7795	$261.78	$261.80	$261.80
Purchase #2	$16.29	9.166%	$17.7831	$17.78	$17.80	$17.80
Purchase #3	$125.25	12.207%	$140.5393	$140.54	$140.55	$140.50
Purchase #4	$25.30	12.786%	$28.5349	$28.53	$28.55	$28.50
Purchase #5	$69.89	11.864%	$78.1817	$78.18	$78.20	$78.20
Purchase #6	$89.98	4.693%	$94.2028	$94.20	$94.20	$94.20
Purchase #7	$103.55	13.284%	$117.3056	$117.31	$117.30	$117.30
7 purchase totals =	$666.76		$738.3269	$738.32	$738.40	$738.30