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	$158.93	10.126%	$175.0233	$175.02	$175.00	$175.00
Purchase #2	$176.53	13.597%	$200.5328	$200.53	$200.55	$200.50
Purchase #3	$133.62	7.282%	$143.3502	$143.35	$143.35	$143.40
Purchase #4	$163.82	6.544%	$174.5404	$174.54	$174.55	$174.50
Purchase #5	$181.83	4.515%	$190.0396	$190.04	$190.05	$190.00
Purchase #6	$38.51	10.385%	$42.5093	$42.51	$42.50	$42.50
Purchase #7	$84.55	6.130%	$89.7329	$89.73	$89.75	$89.70
7 purchase totals =	$937.79		$1,015.7285	$1,015.72	$1,015.75	$1,015.60