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	$53.83	6.679%	$57.4253	$57.43	$57.45	$57.40
Purchase #2	$217.90	3.375%	$225.2541	$225.25	$225.25	$225.30
Purchase #3	$231.35	11.723%	$258.4712	$258.47	$258.45	$258.50
Purchase #4	$125.63	4.820%	$131.6854	$131.69	$131.70	$131.70
Purchase #5	$222.55	4.721%	$233.0566	$233.06	$233.05	$233.10
Purchase #6	$24.32	6.658%	$25.9392	$25.94	$25.95	$25.90
Purchase #7	$128.27	10.862%	$142.2027	$142.20	$142.20	$142.20
7 purchase totals =	$1,003.85		$1,074.0345	$1,074.04	$1,074.05	$1,074.10