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	$137.96	3.154%	$142.3113	$142.31	$142.30	$142.30
Purchase #2	$234.70	4.708%	$245.7497	$245.75	$245.75	$245.70
Purchase #3	$52.92	6.630%	$56.4286	$56.43	$56.45	$56.40
Purchase #4	$229.96	4.715%	$240.8026	$240.80	$240.80	$240.80
Purchase #5	$40.50	13.316%	$45.893	$45.89	$45.90	$45.90
Purchase #6	$169.25	3.664%	$175.4513	$175.45	$175.45	$175.50
Purchase #7	$91.54	11.747%	$102.2932	$102.29	$102.30	$102.30
7 purchase totals =	$956.83		$1,008.9297	$1,008.92	$1,008.95	$1,008.90