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	$80.59	7.765%	$86.8478	$86.85	$86.85	$86.80
Purchase #2	$109.88	3.123%	$113.3116	$113.31	$113.30	$113.30
Purchase #3	$182.41	4.673%	$190.934	$190.93	$190.95	$190.90
Purchase #4	$90.80	6.150%	$96.3842	$96.38	$96.40	$96.40
Purchase #5	$14.28	6.725%	$15.2403	$15.24	$15.25	$15.20
Purchase #6	$124.38	9.697%	$136.4411	$136.44	$136.45	$136.40
Purchase #7	$31.30	3.454%	$32.3811	$32.38	$32.40	$32.40
7 purchase totals =	$633.64		$671.5401	$671.53	$671.60	$671.40