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	$202.99	12.732%	$228.8347	$228.83	$228.85	$228.80
Purchase #2	$120.88	5.476%	$127.4994	$127.50	$127.50	$127.50
Purchase #3	$102.95	6.344%	$109.4811	$109.48	$109.50	$109.50
Purchase #4	$209.86	3.607%	$217.4297	$217.43	$217.45	$217.40
Purchase #5	$174.67	6.568%	$186.1423	$186.14	$186.15	$186.10
Purchase #6	$127.55	10.172%	$140.5244	$140.52	$140.50	$140.50
Purchase #7	$97.87	11.235%	$108.8657	$108.87	$108.85	$108.90
7 purchase totals =	$1,036.77		$1,118.7773	$1,118.77	$1,118.80	$1,118.70