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	$49.98	13.560%	$56.7573	$56.76	$56.75	$56.80
Purchase #2	$49.55	5.552%	$52.301	$52.30	$52.30	$52.30
Purchase #3	$178.55	13.426%	$202.5221	$202.52	$202.50	$202.50
Purchase #4	$217.78	10.290%	$240.1896	$240.19	$240.20	$240.20
Purchase #5	$208.34	12.344%	$234.0575	$234.06	$234.05	$234.10
Purchase #6	$85.84	4.279%	$89.5131	$89.51	$89.50	$89.50
Purchase #7	$198.82	12.524%	$223.7202	$223.72	$223.70	$223.70
7 purchase totals =	$988.86		$1,099.0608	$1,099.06	$1,099.00	$1,099.10