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	$102.99	7.765%	$110.9872	$110.99	$111.00	$111.00
Purchase #2	$164.83	3.369%	$170.3831	$170.38	$170.40	$170.40
Purchase #3	$131.72	8.455%	$142.8569	$142.86	$142.85	$142.90
Purchase #4	$211.79	13.119%	$239.5747	$239.57	$239.55	$239.60
Purchase #5	$175.55	11.824%	$196.307	$196.31	$196.30	$196.30
Purchase #6	$138.52	4.140%	$144.2547	$144.25	$144.25	$144.30
Purchase #7	$47.25	5.846%	$50.0122	$50.01	$50.00	$50.00
7 purchase totals =	$972.65		$1,054.3758	$1,054.37	$1,054.35	$1,054.50