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	$59.35	4.618%	$62.0908	$62.09	$62.10	$62.10
Purchase #2	$170.86	5.176%	$179.7037	$179.70	$179.70	$179.70
Purchase #3	$146.27	13.550%	$166.0896	$166.09	$166.10	$166.10
Purchase #4	$200.86	5.160%	$211.2244	$211.22	$211.20	$211.20
Purchase #5	$179.35	11.420%	$199.8318	$199.83	$199.85	$199.80
Purchase #6	$71.84	9.258%	$78.4909	$78.49	$78.50	$78.50
Purchase #7	$134.72	5.708%	$142.4098	$142.41	$142.40	$142.40
7 purchase totals =	$963.25		$1,039.8410	$1,039.83	$1,039.85	$1,039.80