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	$87.66	4.296%	$91.4259	$91.43	$91.45	$91.40
Purchase #2	$205.97	6.195%	$218.7298	$218.73	$218.75	$218.70
Purchase #3	$73.55	11.377%	$81.9178	$81.92	$81.90	$81.90
Purchase #4	$168.37	6.770%	$179.7686	$179.77	$179.75	$179.80
Purchase #5	$62.30	8.566%	$67.6366	$67.64	$67.65	$67.60
Purchase #6	$71.47	10.383%	$78.8907	$78.89	$78.90	$78.90
Purchase #7	$139.70	13.715%	$158.8599	$158.86	$158.85	$158.90
7 purchase totals =	$809.02		$877.2293	$877.24	$877.25	$877.20