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	$239.78	7.215%	$257.0801	$257.08	$257.10	$257.10
Purchase #2	$152.31	4.322%	$158.8928	$158.89	$158.90	$158.90
Purchase #3	$115.25	3.138%	$118.8665	$118.87	$118.85	$118.90
Purchase #4	$191.29	3.352%	$197.702	$197.70	$197.70	$197.70
Purchase #5	$67.56	5.840%	$71.5055	$71.51	$71.50	$71.50
Purchase #6	$78.98	12.767%	$89.0634	$89.06	$89.05	$89.10
Purchase #7	$239.46	4.812%	$250.9828	$250.98	$251.00	$251.00
7 purchase totals =	$1,084.63		$1,144.0931	$1,144.09	$1,144.10	$1,144.20