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	$67.78	6.627%	$72.2718	$72.27	$72.25	$72.30
Purchase #2	$174.88	13.617%	$198.6934	$198.69	$198.70	$198.70
Purchase #3	$192.83	9.370%	$210.8982	$210.90	$210.90	$210.90
Purchase #4	$212.41	7.557%	$228.4618	$228.46	$228.45	$228.50
Purchase #5	$56.87	9.196%	$62.0998	$62.10	$62.10	$62.10
Purchase #6	$201.66	4.265%	$210.2608	$210.26	$210.25	$210.30
Purchase #7	$102.86	11.387%	$114.5727	$114.57	$114.55	$114.60
7 purchase totals =	$1,009.29		$1,097.2585	$1,097.25	$1,097.20	$1,097.40