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	$131.43	4.491%	$137.3325	$137.33	$137.35	$137.30
Purchase #2	$222.49	6.863%	$237.7595	$237.76	$237.75	$237.80
Purchase #3	$41.63	8.758%	$45.276	$45.28	$45.30	$45.30
Purchase #4	$246.49	4.149%	$256.7169	$256.72	$256.70	$256.70
Purchase #5	$162.59	5.386%	$171.3471	$171.35	$171.35	$171.30
Purchase #6	$12.47	4.698%	$13.0558	$13.06	$13.05	$13.10
Purchase #7	$163.76	9.749%	$179.725	$179.73	$179.75	$179.70
7 purchase totals =	$980.86		$1,041.2128	$1,041.23	$1,041.25	$1,041.20