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	$53.58	4.634%	$56.0629	$56.06	$56.05	$56.10
Purchase #2	$114.47	11.660%	$127.8172	$127.82	$127.80	$127.80
Purchase #3	$172.83	10.550%	$191.0636	$191.06	$191.05	$191.10
Purchase #4	$91.34	11.139%	$101.5144	$101.51	$101.50	$101.50
Purchase #5	$62.59	7.158%	$67.0702	$67.07	$67.05	$67.10
Purchase #6	$160.99	3.686%	$166.9241	$166.92	$166.90	$166.90
Purchase #7	$197.97	5.499%	$208.8564	$208.86	$208.85	$208.90
7 purchase totals =	$853.77		$919.3088	$919.30	$919.20	$919.40